Bilateral Intraocular Transmissible Venereal Tumor (TVT) in a Dog

Abstract

Background: Canine transmissible venereal (TVT) is a transplantable tumor usually transmitted to genital organs during coitus. Tumor cell inoculation is also possible in extragenital sites via licking or sniffing of the vaginal or preputial discharge. Metastases occur predominantly in males involving mainly the regional lymph nodes. On rare occasions, TVT metastases may affect kidney, spleen, tonsils, pancreas, lung, eye, brain, pituitary gland and musculature. Primary ocular involvement of TVT is not commonly reported in dogs, with few cases cited in the literature. The purpose of this study is to describe the ocular manifestations, histological features and immunohistochemical analysis in a canine intraocular TVT.

 Case: A 8-year-old male dog of mixed breed weighing 14.3 kg, was presented because red protrusion from both eyes. After of clinical examination, the dog was submitted to bilateral enucleation. In the histopathological examination was observed tumor cells uniformly round, arranged in solid sheets by delicate connective-tissue stroma. The cells have centrally located round nuclei that contain 1 or 2 prominent nucleolus. The cytoplasm was scant, sometimes contain brown pigment. Immunohistochemical staining with commercially available antibodies such as lysozyme, CD3, CD45R, PAX5 and PNL2 was performed to obtain a more accurate diagnosis. Immunohistochemical staining revealed strong cytoplasmic reactivity to lysozyme in about 90% cells. Weak cytoplasmic immunoreactivity of CD45R was detected in 80-90% of cells and negative immunoreactivity was observed in the CD3, PAX-5, PNL2 antibodies.

Discussion: The use of imunohistochemical markers excluded other types of round cell tumors, such as lymphomas, melanomas, amelanotic melanomas, poorly differentiated carcinomas and mast cell tumors. However, some authors described similar immunostaining in histiocitomas, but the specific staining for Lysozyme, histopathological analisys and immunohistochemical evaluation was fundamental for this diagnosis. As a differential diagnosis for ophthalmic lesions, there are malignant and benign and non-neoplastic neoplastic processes. As malignant neoplasms of intraocular location, there are melanomas, poorly differentiated carcinomas, mast cell tumors. In the case of benign variants, adenomas are highlighted. Round cell neoplasms are also important differential diagnoses, including mast cell tumor, histiocioma, and lymphoma. Non-neoplastic processes, such as granulomatous lesions caused by Leishmaniasis, should also be considered. Linked to this, the performance of immunohistochemistry, due to the range of possible tumor markers, becomes essential for the diagnostic conclusion by excluding other types of round cell tumors, such as lymphoma, melanoma, poorly differentiated carcinomas and mast cell tumors. The prognosis for ocular TVT is good in situations where enucleation occurs, as in this case. That the patient was healthy and in the absence of neoplastic cells due to being affected only in the eye region. Finally, histopathological and imunohistochemistry are examination are confirmatory are the definitive diagnosis. Despite the specific labeling for Lysozyme, it was present in 90% of the cells, and the non-sensitivity of imunoreactivity to CD3 and PAX-5, similar results already described. Thus, and due to the fact that the importance of immunohistochemistry is observed, it suggests - if the use of this technique can validate the confirmation of marking of primary cells of the tumor, in this case reported here.

Keywords:  canine transmissible venereal tumor, intraocular, immunohistochemistry.

Descritores: tumor venéreo transmissível, intraocular, imuno-histoquímica.