Canine transmissible venereal tumor in Morocco: Clinical and pathological findings in 64 dogs-insights from a descriptive epidemiological study (2020-2023)

Abstract

Background: Canine transmissible venereal tumor (CTVT) is a widely spread, contagious neoplasm commonly found in dogs. Mostly affects the external genitalia, however, it may also exhibit unusual clinical presentations.

Aim: To describe the epidemiology, clinical appearance, cytologic and histopathologic features of dogs with TVT in Morocco.

Methods: Within the realm of a nation-wide study on canine and feline tumors in Morocco between September 2020 and March 2023, dogs with histologically diagnosed TVT were identified and data on epidemiologic, clinical as well as cytologic, and histologic features were compiled and analyzed.

Results: A total of 64 cases of canine TVT were diagnosed. 52 dogs were cross-breed (81.2%) while 4 Siberian Huskies (6.2%) and 3 German shepherds (4.7%) were the most affected pure-breed dogs. The median age of dogs at diagnosis was 3 years (range, 1-10years) and male gender was more common (male:female ratio; 1.3:1). Tumor was located exclusively in the genital area in 58 cases (90.6%), whereas 6 dogs (9.4%) had an atypical occurrence of TVT with locations including skin and nasal cavity. Cytology allowed for an early diagnosis in 2 cases. Histology revealed no differences between the genital and extragenital forms. Immunohistochemistry was necessary in 4 cases and revealed positive staining for vimentin and Alpha-1-antitrypsin, negative marking for CD3, CD20, and AE1/AE3, and low cytoplasmic labeling for lysozyme.

Conclusion: CTVT is a widely distributed neoplasm in Morocco, mostly showing presence in young, cross-breed, and oftentimes stray dogs. An adequate understanding of this tumor's epidemiological features is necessary for its management and eradication.

Keywords: Diagnosis; Dogs; Epidemiology; Transmissible venereal tumor.

Fig. 1.. Age distribution of dogs affected with CTVT in this study.

Fig. 2.. Atypical cases of canine transmisible venereal tumour (A) Red, solitary nodule at the left nasal cavity (arrow). (B) Large fistulated mass at the nasal region, causing facial deformation and discharging sanguinopurulent secretion. (C) Ulcerated cutaneous mass at the thoracic region draining a seropurulent secretion. (D) Cytology of extragenital transmissible venereal tumor, nasal mucosa. Presence of a population of round to oval cells, with eccentric nucleus and abundant light basophilic cytoplasm containing the typical intracytoplasmic clear vacuoles of TVT cells (*). Multinucleation (Arrow) and mitotic figures(arrowhead) are frequent. Diff-Quick. Bar = 20 μm.

Fig. 3.. Histological and immunohistochemical characterization of CTVT (A) Histological section shows round neoplastic cells with eosinophilic cytoplasm, arranged in solid sheets and supported by a thin fibrovascular stroma. Mitotic figures are frequent (38 in 2.37mm2). Hematoxylin and Eosin. Bar = 50 μm. (B) Tumor cells are intensely stained with vimentin antibody. ABC method, Mayer’s hematoxylin counterstain. Bar = 50 μm. (C) Majority of neoplastic cells had positive labeling for AAT antibody. ABC method, Mayer’s hematoxylin counterstain. Bar = 50 μm. (D) Poor and variable immunoreactivity with lysozyme antibody is observed. Rare neoplastic cells have positive cytoplasmic labeling (Arrow). Notice intense staining of numerous infiltrative macrophages (Arrowhead). ABC method, Mayer’s hematoxylin counterstain. Bar = 50 μm.