Received: 12/05/2025 Accepted: 26/08/2025 Published: 05/10/2025 1 of 10 https://doi.org/10.52973/rcfcv-e35698 Revista Cientíﬁca, FCV-LUZ / Vol. XXXV ABSTRACT This study aimed to provide data on genital tumors in canines at the Ibn Badis University Hospital Center in Constantine, focusing on tumor localization and histological types in Eastern Algeria. Transmissible venereal tumor, also known as Sticker sarcoma, is a signiﬁcant cancer in dogs, prevalent across all breeds and primarily affecting urban stray populations. It typically manifests as masses on external genital organs but can also appear on other mucous membranes through direct contact. Transmissible venereal tumor predominantly affects dogs aged 2–5 years with high sexual activity; in males, it occurs in the penis and prepuce (6.66%) (8/120), while in females, it affects the posterior vaginal region and vulva (10%) (12/120). Diagnosis is based on clinical history, chronic discharge, typical lesion locations, and histopathological features conﬁrmed by Hematoxylin & Eosin staining. The immunohistochemical analysis used desmin and myogenin to differentiate Transmissible venereal tumor cells and conﬁrm diagnosis. Vincristine chemotherapy remains the primary treatment, often combined with surgery. Key words: Stray dogs; epidemiology; diagnosis; treatment; transmissible venereal tumor; histological type; immunohistochemistry RESUMEN Este estudio tuvo como objetivo proporcionar datos sobre tumores genitales en caninos en el Centro Hospitalario Universitario Ibn Badis de Constantina, centrándose en la localización tumoral y los tipos histológicos en el este de Argelia. El tumor venéreo transmisible, también conocido como sarcoma de Sticker, es un cáncer signiﬁcativo en los perros, prevalente en todas las razas y que afecta principalmente a las poblaciones callejeras urbanas. Generalmente se maniﬁesta como masas en los órganos genitales externos, pero también puede aparecer en otras membranas mucosas por contacto directo. El tumor venéreo transmisible afecta predominantemente a perros de 2 a 5 años con alta actividad sexual; en los machos se localiza en el pene y el prepucio (6,66 %) (8/120), mientras que, en las hembras afecta la región vaginal posterior y la vulva (10 %) (12/120). El diagnóstico se basa en la historia clínica, la secreción crónica, la localización típica de las lesiones y las características histopatológicas confirmadas mediante tinción con Hematoxilina y Eosina. El análisis inmunohistoquímico utilizó desmina y miogenina para diferenciar las células del tumor venéreo transmisible y conﬁrmar el diagnóstico. La quimioterapia con vincristina sigue siendo el tratamiento principal, a menudo combinada con cirugía. Palabras clave: Perros callejeros; epidemiología; diagnóstico; tratamiento; tumor venéreo; tipo histológico; inmunohistoquímica Histopathological characterization of genital tumors, with emphasis on Transmissible Venereal Tumor in the canine species in Eastern Algeria Caracterización histopatológica de los tumores genitales, con énfasis en el tumor venéreo transmisible en la especie canina en el este de Argelia Zahra Gabli 1 , Zouhir Djerrou 1,2 * 1 University 20 August 1955 – Skikda, Faculty of Sciences, Natural and Life Sciences Department. Algeria. 2 University of Mentouri Constantine 1, Institute of Veterinary Sciences, Laboratory of Pharmacology and Toxicology. Algeria. *Corresponding author: zouhir21265@yahoo.fr; z.djerrou@univ–skikda.dz

Histopathological characterization of genital tumors in Canine species / Gabli and Djerrou _________________________________________ 2 of 10 INTRODUCTION Health issues in dogs have long been a concern for those interested in canine health and well–being. The ﬁrst description of transmissible venereal tumor (TVT) was recorded by Blaine in 1810 [1], making it the oldest known contagious cancer in dogs (Canis lupus familiaris), originally emerging over 10,000 years ago [2, 3, 4]. Extensive research has been conducted to understand the origin and evolutionary mechanisms of this disease [2, 5]. Some countries, such as England in the 20 th century, have successfully developed laws and preventive measures against this infectious cancer. Transmissible Venereal Tumor, commonly referred to as “stick tumor,” is also known as canine transmissible venereal sarcoma, infectious sarcoma, or Sticker’s sarcoma [6]. This highly contagious natural cancer is transmitted horizontally [2] during coitus and through direct contact with viable tumor cells across damaged mucosa, including licking, snifﬁng, or grooming [7, 8, 9], and is characterized as a benign round–cell neoplasm in dogs [10]. Initially, a small tumor lesion can progress into a large, ulcerated mass with hemorrhagic discharge and a foul odor, typically localized to the external genital mucosa of both sexes across all breeds. Occasionally, TVT may also be found in the uterus. Transmissible Venereal Tumor is particularly prevalent in dogs aged 2 to 5 years [11, 12, 13], accounting for 23% to 43% of all tumors in dogs, making it the most common tumor in India. Recent epidemiological reviews also conﬁrm that TVT remains one of the most frequent canine neoplasms worldwide [11, 13], with higher prevalence in tropical and subtropical regions [6], primarily affecting populations of unaltered or unsupervised dogs [14]. Both male and female dogs are susceptible, raising global concerns as this benign reticulo–endothelial tumor predominantly affects the external genital mucosa and rarely the internal genital organs [15, 16]. Although tumors can arise at any age, benign tumors are more frequent in younger dogs, while malignant tumors are more prevalent in older dogs [17]. Recent investigations estimate that TVT represents a signiﬁcant proportion of canine tumors, particularly in tropical and subtropical regions, where it continues to pose a major veterinary health problem [18]. Immunocompromised animals are more susceptible to severe manifestations of TVT. Recent genomic investigations have revealed numerous mutations and adaptive mechanisms that enable this cancer to evolve and persist in canine populations [19]. The host’s immune response plays a critical role in tumor progression, with younger, sexually mature animals being more vulnerable as viable tumor cells traverse major histocompatibility complex (MHC) barriers during coitus [19]. Distinct cellular changes have been observed during different stages of tumor development [13]. Over time, downregulation of MHC expression further facilitates horizontal transmission to other dogs [6], although no natural cases have yet been reported in wild canids [20]. TVT is primarily transmitted through sexual contact, affecting the genital system of sexually mature animals. However, neoplasia can also be transferred through licking or snifﬁng, leading to extragenital transmission and, in severe cases, metastasis to internal organs [21]. Tumors in progressive stages exhibit round cells with microvilli, while regressing tumors contain transitional spindle–shaped cells. TVTs can develop slowly or become invasively malignant and metastasize [22]. Loss of mucosal integrity enhances transmission. Sterilization plays a key role in controlling disease spread, although this method has limitations. Initial clinical evaluations can raise strong suspicions, with further analyses aiding in the diagnosis of less evident cases. Several therapeutic options exist, including chemotherapy, which will be detailed, as affected animals generally have a favorable prognosis with low metastatic potential. A recent epidemiological survey updated global data on TVT distribution based on questionnaires sent to veterinary practitioners in the study region. Results indicate that TVT has an endemic evolution in certain geographic areas and is a common disease among dogs worldwide. Its distribution correlates with the presence of free–ranging dogs, with transmission occurring through both mating and experimental cell inoculation. The disease has been reported on all continents, with no race, age, or sex sensitivity identified; however, breeding systems, population density, and uncontrolled contact are signiﬁcant transmission factors, particularly in Africa and Asia, where prevalence exceeds 1% but remains below 10% [23]. In regions like the Bahamas, Japan, and India, it is the most frequent tumor in dogs [24]. Some areas appear free of the disease, likely due to effective management of canine populations, though accurate incidence rates for reproductive tumors are challenging to ascertain due to high rates of castration and lack of histopathological examinations [20]. Only domestic dogs are signiﬁcantly affected by this disease across all breeds [25], primarily among stray or semi–stray populations. In cases involving domestic dogs, 75.5% occurred after an escape episode, with 41.3% being guard dogs and 41.5% hunting dogs. Companion dogs, living indoors and under supervision, account for only 4% of cases [25]. No speciﬁc breed predisposition exists, and the only affected species is the dog [24]. Other wild canids including foxes, coyotes, and wolves have been shown to develop typical CTVT lesions following experimental transplantation of viable tumor cells, but no natural transmission has been documented in these species [26, 27]. The average age of contamination is 3 years, typically between 2 and 5 years, but can range from 2 to 8 years [1, 25]. Sexual maturity and periods of activity are directly linked to this age range. Cases are relatively high among sexually mature dogs, with an incidence of 2% to 43% in temperate regions [28]. Young, sexually immature dogs can still contract the disease through direct contact [29]. Most affected animals are stray dogs, but unspayed females in heat often seek mates, increasing the risk of transmission. If owners opt against sterilization for breeding purposes, they should take precautions to prevent accidents, such as comprehensive genital examinations before breeding, awareness of heat cycles, and proper fencing [29]. While sterilization is crucial in combating Sticker sarcoma, some cases have been reported in operated animals [27]. Natural TVT has frequently been observed in external genital organs [30]. Although there is no speciﬁc predisposition based on age, sex, or breed, larger breeds are often more affected [11, 12] and transmission can occur through licking, biting, and snifﬁng the affected areas. TVT is enzootic in regions with poor breeding control and a high number

_________________________________________________________________________________________________Revista Cientiﬁca, FCV-LUZ / Vol.XXXV 3 of 10 of sexually active free–ranging dogs [11]. Primary extragenital TVT is rare, with the most common sites being the nasal and oral cavities, skin, and rectum. The regional lymph nodes remain the most frequent site of metastasis [31]. Genital TVT often proliferates as a cauliflower–like mass with ulceration, while extragenital forms typically present as nodular or ulcerative lesions, sometimes with multiple lobules or ﬁrm solitary nodules capable of invading the mucosal and submucosal layers [32]. Transmissible venereal tumor is most frequently observed in young adult dogs aged 2–5 years and can spread rapidly within households, even among neutered or spayed animals. Transmission occurs mainly through sexual contact, but also via licking, biting, or snifﬁng the affected regions. Clinically, affected dogs may develop anorexia, dehydration, and progressive polydipsia, while histological examinations of regressing tumors reveal strong T–cell inﬁltration, which promotes regression through immune–mediated differentiation and apoptosis [33, 34]. Risk factors, particularly in females, include poor nutritional status and oxidative stress, which can increase susceptibility and influence tumor progression [35]. The clinical manifestations of TVT usually begin with pruritus, mucosal inflammation, and small gray granulations that evolve into red nodules. These may coalesce into single or multiple masses [35]. Genital TVT typically appears in the penile or preputial regions of males and the vulvar area of females. Affected dogs often lick the tumor, leading to bleeding or discharge. Larger tumors may obstruct urination, while oral lesions can interfere with feeding, and nasal tumors may cause discharge, sneezing, and congestion [35]. Clinical signs vary by tumor location but typically include purulent, bloody discharge from the external genitalia, often accompanied by a foul odor indicating bacterial superinfection, alterations in estrous cycles, and changes in sexual behavior, along with non–speciﬁc symptoms such as abdominal distension, perineal ulceration, tenesmus, dysuria, hematuria, and dermatological changes. Less common signs include lethargy, anorexia, constipation, paraphimosis, refusal to mate, and weight loss [34]. Sticker sarcoma is a histio–round–cell tumor affecting somatic cells most likely of histiocytic or immature myeloid origin and is generally considered low–grade in aggressiveness. It belongs to the broader category of round cell tumors, which includes lymphoma, mastocytoma, histiocytoma, plasmacytoma, and melanoma. Uniquely, the tumor itself is the causal agent, transmitted through the direct transfer of viable neoplastic cells, and thus behaves as a clonally transplanted allograft rather than a virally induced cancer [26, 36, 37, 38, 39]. As a parasite, it can manipulate its host to favor its transmission, potentially affecting sexual receptivity, reproductive cycles, and female preferences [27, 38]. The primary transmission route is mating, where direct transfer of viable cancer cells occurs due to abrasion of contacting genital mucosa [11, 27, 39, 40]. Direct contact with nasal, oral, or ocular mucosa is also possible. Dogs unsupervised outdoors are at higher risk of encountering infected individuals [11, 25, 26, 27, 29]. Symptoms typically appear 2 to 6 months’ post–exposure [11, 41, 42]. Overall, the tumor has minimal impact on the animal’s general health (few systemic repercussions and limited biochemical anomalies). Rare cases of necrotic masses, urethral obstruction, or metastases. The objective of study is to describe the clinical manifestations and the pathological aspects of transmissible venereal tumor cases in dogs. Histology was used to conﬁrm clinical suspicion and highlight the characteristics of the tumor under investigation. Immunohistochemical techniques facilitate the identiﬁcation of the cell type involved in the neoplasm. MATERIALS AND METHODS A total of 120 dogs (Canis lupus familiaris) were presented to Veterinary clinics across various regions of Eastern Algeria between January 2020 and September 2022 for various health issues. Among them, 20 cases (8 males and 12 females) showing lesions of the reproductive system were identiﬁed and selected for this study. The epidemiological proﬁle was assessed through a questionnaire, where owners answered speciﬁc questions to guide the diagnosis. Key questions focused on tumor location, sex, age, breed, onset time of the tumor, sterilization status, medical history, concurrent diseases, and previous treatments. The study included dogs aged between 5 to 8 years, and none of them were sterilized. No breed or sex predisposition was observed, although the condition appears more common in large–breed dogs [19, 32]. For surgical intervention, all animals underwent wide local excision of the tumor, including safety margins, as the standard treatment approach. Prior to surgery, all dogs received a full physical examination and complementary tests, including complete blood counts, biochemical proﬁles, and, when necessary, radiographic and ultrasound examinations. These tests were performed to assess the animals’ general health status and to rule out any contraindications for anesthesia and surgery. However, detailed results of these evaluations are not presented here as they did not reveal any abnormalities relevant to the objective of this study. Surgical procedures were performed using basic soft tissue surgery instruments (Shankang stainless steel surgical kits, Shankang Medical Instrument Co., Ltd., China) under inhalation anesthesia. Anesthesia was delivered using a veterinary inhalation anesthesia machine (YUESHEN YSA-1V, Yuesen Med Equipment Co., Ltd., China). The surgical treatment involved the complete excision of accessible tumor cells, with tumor tissue fragments preserved in 10% formaldehyde for histopathological examination, subject to the owner’s consent. Cytological examination (data not shown) was conducted only in animals clinically suspected of having TVT, as it provided a rapid, low–cost diagnostic aid before histopathological conﬁrmation. Among the 20 dogs studied, 19 cases were diagnosed as TVT, while 1 case corresponded to a vaginal adenocarcinoma. Cytological smears were prepared, stained using a quick Romanowsky–type stain kit (Baso Wright– Giemsa Stain Kit, Baso Diagnostics Inc., China), and examined under a light microscope (Sunny L3000, Ningbo Sunny Instruments Co., Ltd., China). The diagnostic approach for macroscopically identifying Sticker’s sarcoma is based on a clinical examination of the animal, which includes both a general and individual assessment of the health status of all dogs, even those without speciﬁc clinical signs. Initially, data are collected through history–taking and case reviews, followed by general clinical data such as temperature, heart and respiratory rates, mucosal status, and lymph node condition. This

Histopathological characterization of genital tumors in Canine species / Gabli and Djerrou _________________________________________ 4 of 10 step is followed by a specialized examination focused on inspecting the genital area in both sexes to determine tumor location, size, shape, color, consistency, and adhesion [11, 25, 41]. The clinical signs of TVT in dogs are depicted in FIGS. 1–8 for both male (FIGS. 1, 2, and 3) and female (FIGS. 4, 5, 6, 7, and 8) dogs. The aggressive character of the lesion is demonstrated by the hemorrhaged, ulcerated, and inflamed nodule on a male dog’s penile region in FIG. 1. A large, hard mass at the base of the penis with numerous regions of ulceration and inflammation, indicative of advanced TVT, is shown in FIGS. 2 A and B. Hemorrhagic, polypoid tumors on the prepuce and penis mucosa are and which also shows the tumor’s characteristic friable and vascularized surface. A nodular lesion with a hard, bell–clapper–like appearance in females is depicted in FIGS. 3 A and B, suggesting deep tissue invasion. A polyploid tumor that resembles cauliflower and is prone to bleeding and bruises is seen in 3B, the soft, reddish–violet vegetal mass with incomplete pedunculation in FIGS. 4 A and B, is typical of the vaginal vestibule as TVT progresses. A big, friable, hemorrhagic, pedunculated mass with lobulated structure is depicted in 4B, which frequently causes discomfort and secondary infections. A polyploid, hemorrhagic, and ulcerated mass in the vaginal vestibule with lesion extension into the breast region is shown in FIG. 5, indicating local invasion outside of the genital canal. Although the image does not clearly show the penile lesion due to technical limitations at the time of capture, it illustrates the clinical presentation of an affected patient. More detailed gross lesions are shown in FIGS. 2 to 5. Histopathological technique The study focused on tumor samples from the genital tract obtained during surgical procedures in both male and female dogs (FIGS. 6 A and B). These samples were processed at the histopathology laboratory of Ibn Badis Hospital in Constantine and classiﬁed according to their nature, anatomical site, and breed. A routine histopathological examination using the Hematoxylin & Eosin (HE) method was performed on the collected tissue fragments to establish the diagnosis, particularly to conﬁrm cases of TVT and to identify other genital tumor types. FIGURE 1. External view of a male dog aﬀected by TVT 2A 2B 3A FIGURE 2. A: Mass at the base of the penis showing ulcerated and inﬂamed areas, consistent with advanced transmissible venereal tumor. B: Polypoid lesion of the penis and prepuce with a friable, vascularized surface. Image quality is limited and does not allow detailed appreciation of all features, but the photographs are included for illustrative purposes

_________________________________________________________________________________________________Revista Cientiﬁca, FCV-LUZ / Vol.XXXV 5 of 10 RESULTS AND DISCUSSIONS Histopathological analyses Clinical history, clinical signs, and cytological characteristics often provide useful information, but the deﬁnitive diagnosis of genital tumors was established through histopathological examination. Tissue samples were processed, sectioned, and stained with HE, and diagnoses were made based on the morphological characteristics observed under light microscopy. Vaginal tumors are the second most common reproductive tumors in female dogs, following mammary tumors. The two most frequently encountered types of vaginal tumors are leiomyomas (or ﬁbromas), which develop from smooth muscle, and transmissible venereal tumors, also known as Sticker sarcomas. Fibromas or ﬁbropapillomas, also referred to as vaginal polyps, are benign tumors that occur during the late stages of the estrous cycle. Histologically, Sticker sarcoma consists of cells arranged or grouped in chains, interspersed with delicate connective tissue stroma when stained with HE. Tumor cells are typically arranged radially around blood and lymphatic vessels and exhibit a high nucleus–to–cytoplasm ratio, with rounded nuclei and chromatin ranging from ﬁne to coarse, along with prominent nucleoli. These 3B 3B 4A 4B FIGURE 3. A: Inﬂamed nodule with a hard and ﬁrm appearance resembling a bell clapper. Demonstrates a typical ﬁrm lesion found in female dogs, suggestive of deeper tissue penetration. B: Polyploid appearance resembling cauliﬂower, friable and easily bruised. Shows the irregular, fragile tumor surface often associated with increased risk of trauma and bleeding FIGURE 4. A: Hemorrhagic, red–violet mass with partial pedunculation, located in the vaginal vestibule. Due to deformation and image cropping, the exact anatomical location is not fully appreciable, but the picture illustrates the gross aspect of the lesion. B: Mass larger, friable, red, hemorrhagic, and with a pedunculated appearance. Emphasizes the size and fragile texture of advanced tumors, prone to secondary infection and discomfort FIGURE 5. Tumoral mass with a polypoid and ulcerated appearance, located in the vaginal vestibule of a female dog, with extension toward adjacent tissues. The image illustrates the gross morphology of the lesion, although the anatomical details are diﬃcult to appreciate due to image quality and cropping limitations

Histopathological characterization of genital tumors in Canine species / Gabli and Djerrou _________________________________________ 6 of 10 cells contain a large amount of slightly eosinophilic cytoplasm with poorly deﬁned boundaries. The tumor can be classiﬁed according to stages of development and phases of initial or final progression or regression. The progression phase shows round cells diffusely arranged, separated by delicate connective stroma, with frequent mitotic structures. In the initial regression phase, lymphocytes inﬁltrating the tumor appear and are widely distributed or associated with the stroma. The ﬁnal regression phase involves the collapse of neoplastic tissue and the frequent presence of apoptotic bodies. According to the histological classiﬁcation of tumors in the genital system [42], two histological types of genital tumors were identiﬁed in both sexes (FIGS. 7 and 8). Optical microscopy observation at 400x magniﬁcation after HE staining of a transmissible venereal tumor located in the vagina and penis. The tumor displays a sheet–like proliferation of monomorphic round to polyhedral tumor cells, generally arranged radially around blood and lymphatic vessels, featuring basophilic and vacuolated cytoplasm (red arrow). The cells have large, round vesicular nuclei with variably organized chromatin that can appear dusty or granular, with well–deﬁned nucleoli (yellow arrow). These cells are separated by sparse, well–vascularized connective stroma (green arrow) and form clusters with the presence of capillaries (black arrow). The mitotic index is high, and pleomorphism is also observed (brown arrow), while the epithelial surface is often hyperplastic and ulcerated. The carcinoma shows an inﬁltrative proliferation of tubular and canalicular structures, varying in shape and size (red arrow). The tumor cells are cylindrical with abundant eosinophilic cytoplasm (green arrow) and large hyperchromatic nuclei, exhibiting moderate mitotic activity (brown arrow). Solid tumor foci organized in clusters centered around necrosis are also observed (black arrow). In this study, no other histological types of genital tumors were identiﬁed beyond TVT and adenocarcinoma. Although leiomyomas and ﬁbromas are frequently reported in the literature as common vaginal tumors, they were not observed among our cases. FIGURE 6. A: Removed tumoral mass from a male dog’s penile area. A recently removed tumor mass from a male dog’s penis is depicted in this image. The lesion’s lobulated, vascularized appearance, uneven surfaces, and necrotic patches are all in line with the general appearance of a TVT. B: Tumoral tissue excised from a female dog’s vaginal vestibule. A surgical specimen taken from a female dog’s vaginal vestibule is seen in this picture. The mass exhibits characteristics of an advanced TVT, including being polypoid, soft, and hemorrhagic 6A 6B A (HE 400×) B (HE 100×) C (HE 400×) D (HE 100×) FIGURE 7. Histological section of Canine TVT (Sticker Sarcoma) in male dog (A – B) female dog (C – D). HE: Hematoxylin–eosin

_________________________________________________________________________________________________Revista Cientiﬁca, FCV-LUZ / Vol.XXXV 7 of 10 Complementary techniques in histology: Immunohistochemistry The interpretation of immunostaining analysis is based on both the intensity and quality of membranous staining, determining the percentage of labeled cells in relation to all cancerous cells within the invasive component, and assessing the average intensity of this staining. Myogenin and Desmin are transcription factors considered sensitive and speciﬁc IHC markers for Sticker’s sarcoma. The immunohistochemical results for Sticker’s sarcoma reveal a strongly positive brown staining with the desmin marker (A and B), while the myogenin marker (C and D) exhibits a less intense brown staining in epithelial cells. Utilizing these antibodies enhances diagnostic precision for Sticker’s sarcoma and will ultimately improve the characterization of the disease’s biological behavior and clinical outcomes (FIG. 9). Retrospective studies in oncology are important for identifying certain characteristics of tumors, their biological behavior, and factors that may potentially affect responses to various treatments, thus posing a therapeutic challenge [43]. This study reports a variety of information related to sexual and racial predisposition as well as the age of dogs affected by genital tumors, in association with the histological type and location of these tumors, which aligns with ﬁndings from other authors. In the current study, most of the affected dogs were older than ﬁve years (74%), and the majorities were mixed–breed (59.8%), followed by German Shepherds (38.2%). Some researchers have reported that dogs aged 2 to 5 years are susceptible to venereal tumors [11], which contrasts with our ﬁndings that dogs over ﬁve years old (74%) were the most affected, with mixed–breed dogs (59.8%) being the most prevalent. According to some sources [44], in certain regions where dog breeding is poorly controlled and where stray dogs are in high concentration (urban areas), Sticker sarcoma is the most common canine tumor. Signiﬁcant rainfall and average annual temperature are positively correlated with prevalence. Generally, the main breeds exhibiting genital tumors include the German Shepherd, Poodle, Boxer, and Yorkshire Terrier [45]. In this study, related breeds showed signiﬁcant prevalence, but did not surpass the high incidence found in mixed–breed animals. Overall, the incidence of venereal tumors is more frequent in sexually active dogs. The disease is classiﬁed as high in certain dog breeds in tropical and subtropical countries [11, 46]. Cases of venereal tumors are found in some countries in South and Central America, Africa, and Asia. Venereal tumors are endemic in at least 90 countries worldwide [27]. The global spread of venereal tumors indicates that most dog breeds, regardless of sex and age, can be infected by this disease [11]. A comparative analysis between male and female dogs regarding the most affected reproductive organs revealed that the incidence of vulvo–vaginal tumors (12 out of 120, 10%) is signiﬁcantly higher than that of other organs. Likewise, the number of females (12 out of 20, 60%) presenting genital tumors in our study exceeded that of affected males (8 out of 20, 40%). These results corroborate reports from various authors [47, 48]. TVT is most often spread during coitus through the transfer of neoplastic cells from one dog to another, rather than by cellular transformation in the affected host [49]. This unique mode of transmission, by allografting, has been widely reported [44]. Clinical signs are less pronounced in males, where the tumor may be discovered incidentally, which aligns with our observations. In our study, tumor masses resembling cauliflower, friable and vascularized, were observed in the vaginas and vulvas of female dogs, while other masses were located on the penile area of male dogs. TVT typically presents with extragenital masses associated with serohemorrhagic discharge, with tumor mass sizes ranging from 2 to 10 cm. The tumors observed in this study exhibited the same macroscopic characteristics reported in prior studies [29, 44]. The following results pertain to animals where histopathological examination can be used to conﬁrm the diagnosis of TVT. The genital tract is a complex system composed of various organs A (Desmin 400×) B (Desmin 100×) C (Myogenin 400×) D (Myogenin 100×) A (HE 400×) B (HE 100×) FIGURE 8. Histopathological features of an adenocarcinoma in the vaginal area of a female dog. HE: Hematoxylin–eosin FIGURE 9. Immunohistochemical staining of Sticker sarcoma: A strong brown positive staining is observed with the desmin marker (A and B), while the myogenin marker (C and D) shows a less intense brown staining in the epithelial cells using Harris hematoxylin

Histopathological characterization of genital tumors in Canine species / Gabli and Djerrou _________________________________________ 8 of 10 capable of generating different types of tumors, which is why the reproductive system of dogs shows varying incidences based on the tumor’s origin. TVT is a common tumor of the external genital organs in young, stray, and sexually active animals [50]. The following results pertain to animals where histopathological examination conﬁrmed the diagnosis of TVT. The genital tract is composed of various organs capable of generating different tumor types; however, in this study, the tumors were restricted to the external genital organs. Among the 120 dogs examined, 20 cases of genital tumors were selected, with 12 out of 20 (60%) females showing the highest prevalence compared to 8 out of 20 (40%) males. In the male reproductive system, the most frequently found histological type was penile Sticker sarcoma (6.66%). In females, the most common histological types were vulvar and vaginal TVT and vaginal adenocarcinoma [11, 48, 49]. Chemotherapy with vincristine sulfate is the treatment of choice for transmissible venereal tumor and has been documented for decades as the most effective approach, with high remission rates and low recurrence [44]. Surgical excision, while sometimes used, carries a signiﬁcant risk of relapse because TVT is a transplantable tumor and residual cells can easily remain at surgical margins. In this cases, vincristine was not available in Algeria; therefore, surgery was performed as an alternative, although the limitations of this approach are acknowledged. Canine transmissible venereal tumor is generally considered a curable cancer when appropriate protocols are applied. Nonetheless, rare cases of metastasis, drug resistance, or fatal outcomes have been reported in endemic areas, particularly among immunocompromised dogs. Chemotherapy remains the treatment of choice, with vincristine sulfate (0.5–0.7 mg·m² IV, once weekly for 3–6 weeks) being highly effective. Alternative protocols combining vincristine with cyclophosphamide or methotrexate have also demonstrated favorable outcomes [11]. Surgical excision alone is less satisfactory because of the high recurrence risk associated with the transplantable nature of this tumor. Canine transmissible venereal tumor is highly responsive to vincristine sulfate chemotherapy, which remains the treatment of choice. Recent studies conﬁrm remission rates above 95% when vincristine is administered weekly for 4–8 sessions. Combination protocols, including the use of intratumoral Bacillus Calmette– Guérin (BCG) with vincristine, have also shown enhanced tumor regression and improved immune response, although they are less frequently applied in clinical practice [51, 52]. CONCLUSIONS In this study, genital tumors in dogs were limited to the external genital organs, with TVT being the most frequently diagnosed lesion. Histopathology proved essential for conﬁrming the diagnosis and characterizing tumor types. Although surgery was performed due to the unavailability of vincristine in Algeria, chemotherapy remains the treatment of choice because of its high efﬁcacy and lower recurrence rates. These ﬁndings underline the importance of systematic diagnosis and appropriate therapy in managing canine genital tumors. Conflict of interest The authors declare that they have any conflict of interest. BIBLIOGRAPHIC REFERENCES [1] Crozet G. Naturally transmissible tumors: bibliographic synthesis [doctoral thesis on the Internet]. Maisons–Alfort (France): National Veterinary School of Alfort; 2018 [cited June 25, 2025]. 137 p. Available from: https://goo.su/bYnPdL [2] Ostrander EA, Davis BW, Ostrander GK. Transmissible tumors: breaking the cancer paradigm. Trends Genet. [Internet]. 2016; 32(1):1–15. doi: https://doi.org/f762ft [3] Ugochukwu ICI, Agina OA, Omeke JN, Aneke CI, Adamu LF, Ajayi OL, Giginya NI, Ihedioha JI, Njoku CI, Sackey AKB. An appraisal of Canine transmissible venereal tumour with emphasis on molecular biology and pathology. Thai J. Vet. Med. [Internet]. 2025 [cited Apr. 12, 2025]; 50(1):1–12. Available from: https://goo.su/zeKFqE6 [4] Pimentel PAB, Giuliano A, Odatzoglou P, Ignatenko N, Wenceslau RR, Almeida IO, da Silva PHS, Costa MdP, Horta RS. Clinical guidelines for canine transmissible venereal tumour treatment: Systematic review and meta–analysis. Vet. Comp. Oncol. 2025; 23(2):125–140. doi: https://doi.org/pprn [5] Oruç E, Sağlam YS, Cengiz M, Polat B. Bir Köpekte Bulaşıcı Venereal Tümör Meme Metastazının İnce İğne Aspirasyonu ile Sitolojik Teşhisi ve Vincristine Sülfat ile Tedavisi [Cytological diagnosis of breast metastasis of transmissible venereal tumor by fine needle aspiration and the treatment with vincristine sulfate in a dog]. Atatürk Üniversitesi Vet. Bilim. Derg. [Internet]. 2011 [cited Apr. 12, 2025]; 6(1):63–69. Turkish. Available from: https://goo.su/6NdEc [6] Laissaoui N, Millán Y, Simon Betz D, El Mrini M, Bouayad G, Lamalmi N, Tligui N, Azrib R. Canine transmissible venereal tumour in Morocco: Clinical and pathological ﬁndings in 64 dogs – insights from a descriptive epidemiological study (2020-2023). Open Vet. J. [Internet]. 2024; 14(5):1206– 1215. doi: https://doi.org/pprp [7] Bendas AJR, Moreto PLN, Coxo AB, Holguin PG, Soares DV. Intra–abdominal transmissible venereal tumor in a dog: a case report. Braz. J. Vet. Med. [Internet]. 2022; 44:e001422. doi: https://doi.org/p6nb [8] Da Silva DM, Oliveira MS, Franciosi AL, Belo CEP, Gonçalves KA, De Souza RS, Guérios SD. Treatment of canine transmissible venereal tumor using L–asparaginase, prednisone, and surgery in a clinical chemotherapy–resistant case. Turk. J. Vet. Anim. Sci. 2014; 38(2):220–223. doi: https://doi.org/p6nc [9] Birhan G, Chanie M. A review on canine transmissible venereal tumor: from morphologic to biochemical and molecular diagnosis. Acad. J. Anim. Dis. 2015; [cited Apr. 13, 2025]; 4(3):185–195. Available from: https://goo.su/Z8lEXw [10] Castro KF, Strakova A, Tinucci–Costa M, Murchison EP. Evaluation of a 125 genetic assay for canine transmissible venereal tumour diagnosis in Brazil. Vet. Comp. Oncol. [Internet]. 2017; 15(2):615-618. doi: https://doi.org/f959mr [11] Kumar A, Jadon NS, Zaidi MGH, Kandpal M, Saini R. Transmissible venereal granuloma invasiveness and response to chemotherapeutics in canine. Int. J. Contemp. Res. Multi. [Internet]. 2024; 3(3):140-147. doi: https://doi.org/p6rc

_________________________________________________________________________________________________Revista Cientiﬁca, FCV-LUZ / Vol.XXXV 9 of 10 [12] Amaral AS, Bassani–Silva S, Ferreira I, da Fonseca LS, de Andrade FH, Gaspar LFJ, Rocha NS. Cytomorphological characterization of transmissible canine venereal tumor. Rev. Port. Cienc. Vet. [Internet]. 2007 [cited Apr. 18, 2025]; 102(563–564):253–260. Available from: https://goo.su/X1r1d [13] Abedin SN. Canine transmissible venereal tumor: A review. J. Entomol. Zool. Stud. [Internet]. 2020; 8(2):596-599. doi: https://doi.org/p6nj [14] Den Otter W, Hack M, Jacobs JJL, Tan JFV, Rozendaal L, Van Moorselaar RJA. Effective treatment of transmissible venereal tumors in dogs with vincristine and IL-2. Anticancer Res. 2015 [cited Apr. 18, 2025]; 35(6):3385–3391. Available from: https://goo.su/vNlv [15] Sankar P, Ramya R, Mohamed Ali MG. Therapeutic management of intranasal transmissible venereal tumour in a dog. Intas. Polivet. 2016 [cited Apr. 18, 2025]; 17(2):543– 545. Available from: https://goo.su/H3nFUU [16] Ganguly B, Das U, Das AK. Canine transmissible venereal tumour: A review. Vet. Comp. Oncol. [Internet]. 2016; 14(1):1–12. doi: https://doi.org/pprh [17] Priyadarshini N, Das DP, Panda SK, Samal L. Transmissible venereal tumours (TVT) in bitches: A haematological, biochemical and histopathological study. J. Entomol. Zool. Stud. 2021; 9(1):490-493. doi: https://doi.org/p6pc [18] Ke CH, Tomiyasu H, Lin YL, Huang WH, Huang HH, Chiang HC, Lin CS. Canine transmissible venereal tumour established in immunodeﬁcient mice reprograms the gene expression proﬁles associated with a favourable tumour microenvironment to enable cancer malignancy. BMC Vet. Res. [Internet]. 2022; 18:4. doi: https://doi.org/p6pd [19] Murchison EP. Cancer: Transmissible tumours under the sea. Nature [Internet]. 2016; 534:628–629. doi: https://doi.org/p6pf [20] Morris K, Belov K. Does the devil facial tumour produce immunosuppressive cytokines as an immune evasion strategy? Vet. Immunol. Immunopathol. [Internet]. 2013; 153(1–2):159–164. doi: https://doi.org/p6pk [21] Murchison EP, Wedge DC, Alexandrov LB, Fu B, Martincorena I, Ning Z, Tubio JMC, Werner EI, Allen J, de Nardi AB, Donelan EM, Marino G, Fassati A, Campbell PJ, Yang F, Burt A, Weiss RA, Stratton MR. Transmissible dog cancer genome reveals the origin and history of an ancient cell lineage. Science [Internet]. 2014; 343(6169):437–440. doi:https://doi.org/q7r [22] Decker B, Davis BW, Rimbault M, Long AH, Karlins E, Jagannathan V, Reiman R, Parker HG, Drögemüller C, Corneveaux JJ, Chapman ES, Trent JM, Leeb T, Huentelman MJ, Wayne RK, Karyadi DM, Ostrander EA. Comparison against 186 canid whole–genome sequences reveals survival strategies of an ancient clonally transmissible canine tumor. Genome Res. [Internet]. 2015; 25(11):1646–1655. doi: https://doi.org/f7xspm [23] Siddle HV, Kreiss A, Tovar C, Yuen CK, Cheng Y, Belov K, Swift K, Pearse A–M, Hamede R, Jones ME, Skjødt K, Woods GM, Kaufman J. Reversible epigenetic down–regulation of MHC molecules by devil facial tumor disease illustrates immune escape by a contagious cancer. Proc. Natl. Acad. Sci. USA. [Internet]. 2013; 110(13):5103–5108. doi: https://doi.org/kr7 [24] Strakova A, Murchison EP. The changing global distribution and prevalence of canine transmissible venereal tumour. BMC Vet. Res. [Internet]. 2014; 10:168. doi: https://doi.org/f6fp4q [25] Ke CH, Tomiyasu H, Lin YL, Huang WH, Huang HH, Chiang HC, Lin CS. Canine transmissible venereal tumour established in immunodeﬁcient mice reprograms the gene expression proﬁles associated with a favourable tumour microenvironment to enable cancer malignancy. BMC Vet. Res. [Internet]. 2022; 18(1):4. doi: https://doi.org/p6pd [26] Fonclara E, Goullet P. A case of canine transmissible venereal tumor in a young dog. Point Vet. 2017 [cited Apr. 18, 2025]; 48(377):12-15. Available from: https://goo.su/s6mqJbv [27] Baştan A, Acar DB, Cengiz M. Uterine and ovarian metastasis of transmissible venereal tumor in a bitch. Turk. J. Vet. Anim. Sci. 2008 [cited 18 Apr 2025]; 32(1):65–66. Available from: https://goo.su/vDB8bqk [28] Mirza U, Farooq UB, Makhdoomi DM. Canine transmissible venereal tumor: etiopathology, transmission and treatment. Asian J. Anim. Vet. Adv. [Internet]. 2022 [cited Apr. 12, 2025]; 17(2):39-43. Avaliable in: https://goo.su/fnNhB [29] Bandaranayaka BMLN, Kabilan S, Perera KARK, Abeykoon C, Wijewardena KAN, Ariyarathn HMS. Extragenital canine transmissible venereal tumours: A case series. Sri Lanka Vet. J. [Internet]. 2023; 70(1):27-32. doi: https://doi.org/p6rq [30] do Prado Duzanski A, Flórez LMM, Fêo HB, Romagnoli GG, Kaneno R, Rocha NS. Cell–mediated immunity and expression of MHC class I and class II molecules in dogs naturally infected by canine transmissible venereal tumor: Is there complete spontaneous regression outside the experimental CTVT? Res. Vet. Sci. [Internet]. 2022; 145:193-204. doi: https://doi.org/p6rv [31] Aydın İ, Bülbül A, Avcı GE, Celik HA. Serum oxidative status and adenosine deaminase activity in dogs with transmissible venereal tumour. Bull. Vet. Inst. Pulawy [Internet]. 2009 [cited Apr. 18, 2025]; 53:771–774. Available from: https://goo.su/ tcUWs [32] Blanca PM, María Luisa FR, Guadalupe M, Fátima CL. Oxidative stress in canine diseases: A comprehensive review. Antioxidants. [Internet]. 2024; 13(11):1396. doi: https://doi.org/p6rw. [33] Küçükbekir CN, Günay Uçmak Z, Tek C. Canine transmissible venereal tumor: Etiology, diagnosis, and treatment. J. Istanbul Vet. Sci. [Internet]. 2021; 5(1):57-65. doi: https://doi.org/p6p7 [34] Simoni R, Knoll JC. Clinical Exposures: Canine transmissible venereal tumor – the cytologic clues. Vet. Med. [Internet]. 2008 [cited Apr. 18, 2025]; 103(6):296-304. Available from: https://goo.su/cSYqdYC [35] Baez–Ortega A, Gori K, Strakova A, Allen JL, Allum KM, Bansse– Issa L, Bhutia TN, Bisson JL, Briceño C, Castillo Domracheva A, Corrigan AM, Cran HR, Crawford JT, Davis E, de Castro KF, de Nardi AB, de Vos AP, Delgadillo Keenan L, Donelan EM, Espinoza Huerta AR, Faramade IA, Fazil M, Fotopoulou E, Fruean SN,

Histopathological characterization of genital tumors in Canine species / Gabli and Djerrou _________________________________________ 10 of 10 Gallardo–Arrieta F, Glebova O, Gouletsou PG, Häfelin Manrique RF, Henriques JJGP, Horta RS, Ignatenko N, Kane Y, King C, Koenig D, Krupa A, Kruzeniski SJ, Kwon Y–M, Lanza–Perea M, Lazyan M, Lopez Quintana AM, Losfelt T, Marino G, Martínez Castañeda S, Martínez–López MF, Meyer M, Migneco EJ, Nakanwagi B, Neal KB, Neunzig W, Ní Leathlobhair M, Nixon SJ, Ortega–Pacheco A, Pedraza–Ordoñez F, Peleteiro MC, Polak K, Pye RJ, Reece JF, Rojas Gutierrez J, Sadia H, Schmeling SK, Shamanova O, Sherlock AG, Stammnitz M, Steenland–Smit AE, Svitich A, Tapia Martínez LJ, Thoya Ngoka I, Torres CG, Tudor EM, van der Wel MG, Viţălaru BA, Vural SA, Walkinton O, Wang J, Wehrle–Martinez AS, Widdowson SAE, Stratton MR, Alexandrov LB, Martincorena I, Murchison EP. Somatic evolution and global expansion of an ancient transmissible cancer lineage. Science [Internet]. 2019; 365(6452): eaau9923. doi: https://doi.org/ gg6qqw [36] Cohen D. The canine transmissible venereal tumor: a unique result of tumor progression. Adv. Cancer Res. [Internet]. 1985; 43:75–112. doi: https://doi.org/dr42n9 [37] Martins MIM, Souza FF, Gobello C. The canine transmissible venereal tumor: etiology, pathology, diagnosis and treatment. Adv. Small Anim. Reprod. [Internet]. 2005 [cited Apr. 18, 2025]; 25-32. Available from: https://goo.su/1cCo1 [38] Kennedy JR, Yang TJ, Allen PL. Canine transmissible venereal sarcoma: electron microscopic changes with time after transplantation. Br. J. Cancer. [Internet].1977; 36(3):375– 385. doi: https://doi.org/b9z6k2 [39] Marchal T, Chabanne L, Kaplanski C, Rigal D, Magnol JP. Immunophenotype of the canine transmissible venereal tumour. Vet. Immunol. Immunopathol. [Internet]. 1997; 57(1–2):1–11. doi: https://doi.org/b3sctw [40] Lorimier LP, Fan TM. Canine transmissible venereal tumor. In: Withrow SJ, Vail DM, Page RL, editors. Withrow and MacEwen’s Small Animal Clinical Oncology. 4 th ed. 2007; St. Louis (USA): Saunders Elsevier. p. 799–804. [41] McEntee MC. Reproductive oncology. Clin. Tech. Small Anim. Pract. [Internet]. 2002; 17(3):133–149. doi: https://doi.org/ cw75kj [42] Den Otter W, Hack M, Jacobs JJL., Tan JFV, Rozendaal L, Van Moorselaar JA. Effective treatment of transmissible venereal tumors in dogs with vincristine and IL2. Anticancer Res. 2015 [cited Apr. 18, 2025]; 35(6):3385–3391. PMID: 26026076. Available from: https://goo.su/ozWbc8 [43] Souza JRST, Camarão AP, Rego LC. Ruminal degradability of dry matter and crude protein of agroindustry, ﬁsh and slaughterhouse byproducts in goats. Braz. J. Vet. Res. Anim. Sci. [Internet]. 2000 [cited Apr. 18, 2025]; 37(2):144–150. Available from: https://goo.su/UmBIe [44] Stockmann D, Ferrari HF, Andrade AL, Lopes RA, Cardoso TC, Luvizotto MCR. Canine transmissible venereal tumors: Aspects related to programmed cell death. Braz. J. Vet. Pathol. [Internet]. 2011 [cited Apr. 18, 2025]; 4(1):67–75. Available from: https://goo.su/CU8C [45] MacLachlan NJ, Kennedy PC. Tumors of the genital systems. In: Meuten DJ, editor. Tumors in Domestic Animals, 4 th ed. Iowa (USA): Iowa State Press. 2002; p. 547–573. [46] Veloso JF, Oliveira TN, Andrade LP, Silva FL, Sampaio KMOR., Michel AFRM, Lavor MSL, Carlos RSA. Three cases of exclusively extragenital canine transmissible venereal tumor (cTVT). Acta Sci. Vet. [Internet]. 2018; 46:8. doi: https://doi.org/p6p8 [47] Boyé P, Benoit J. Les tumeurs vénériennes transmissibles canines. Le Point Vétérinaire Expert Canin. 2016 [cited Apr. 18, 2025]; 364. Available from: https://goo.su/iupehA [48] Liptak JM, Christensen NI. Soft tissue sarcomas. In: Vail DM, Thamm DH, Liptak JM, editors. Withrow & MacEwen’s Small Animal Clinical Oncology. 6 th ed. 2019; New York (USA): Saunders, p. 404–431. [49] Rogers KS, Wantschek L, Lees GE. Diagnostic evaluation of the canine prostate. Compend. Contin. Educ. Pract. Vet. 1986; 8(11):799–811. [50] Morgan E, O’Riordan RM, Kelly TC, Culloty SC. Influence of disseminated neoplasia, trematode infections and gametogenesis on surfacing and mortality in the cockle Cerastoderma edule. Dis. Aquat. Organ. 2012; 98(1):73–84. doi: https://doi.org/fg4j66 [51] Amrutha VS, Rajimon KT, Prakash AK, Viswanathan CK, Sulabha G, Jithil VR. Therapeutic management of canine transmissible venereal tumor associated Phimosis in a dog. Int. J. Vet. Sci. Anim. Husb. [Internet]. 2023 [cited Apr. 22, 2025]; 8(5):467-469. https://goo.su/PU3C4aR [52] Tella MA, Ajala OO, Taiwo VO. Complete regression of transmissible venereal tumour (TVT) in Nigerian mongrel dogs with vincristine sulfate chemotherapy. Afr. J. Biomed. Res. 2004; 7(3):133–138. doi: https://doi.org/b83bbh