Cutaneous Epitheliotropic Lymphoma in a Lhasa Apso

Background: Lymphoma neoplasms originate from the lymphocytes. Anatomically, these tumors can be classified into multicentric, digestive, mediastinal, and cutaneous forms. The etiology of cutaneous lymphoma remains unclear; however, it has been associated with chronic skin inflammation. The definitive diagnosis is based on histological analysis and immunohistochemistry, although fine-needle aspiration cytology has shown good results. The aim of this paper is to describe the clinicopathological aspects of a case of cutaneous epitheliotropic T cell lymphoma, classified as mycosis fungoides, in a Lhasa Apso dog. Case: A 8-year-old bitch Lhasa Apso with multiple non-pruritic skin nodules and history of 10-day evolution was referred to the Veterinary Hospital of the Centro Universitário do Espírito Santo (UNESC), Colatina, ES, Brazil. The nodules were erythematous, exophytic, firm, circumscribed, and measured 0.2-4 cm in diameter in locations throughout the animal's body. An incisional biopsy was performed with an 8-mm punch and sent for histopathological examination. An infiltrative, poorly demarcated, non-encapsulated, densely cellular neoplasm, which was replacing the dermal collagen and displacing the adnexa, was observed in the dermis. The tumor was composed of a population of round cells, with generally distinct cell borders and a small-to-moderate amount of eosinophilic cytoplasm. The nuclei were irregularly rounded and occasionally edentulous, with vesicular chromatin, a visible nucleus, and 11 mitotic figures in an area of 2.37 mm². The immunohistochemical test, which was positive for the CD3 marker, confirmed the diagnosis of T cell lymphoma. On an ultrasound to identify metastasis, the liver showed heterogeneous parenchyma, heterogeneous expansive formation, areas of cavitary appearance, and cytology compatible with lymphoma. Discussion: A diagnosis of the mycosis fungoides type of cutaneous epitheliotropic T cell lymphoma was established based on clinical, laboratory, anatomopathological, and immunohistochemical findings. Pruritus is a common clinical condition in animals with mycosis fungoides, particularly in those with the erythrodermic form of the disease. Epitheliotropic lymphomas have no sexual or racial predilections and usually affect dogs over 9 years of age. The Cocker Spaniel, English Bulldog, Boxer, Golden Retriever, Scottish Terrier, Briard, English Springer Spaniel, Beagle, German Shepherd, and English Cocker Spaniel breeds are frequently affected by these lymphomas. These neoplasms can have a primary skin origin, or they can be secondary and associated with lymphoma found elsewhere in the body. Chemotherapy is the treatment of choice, especially in cases with multifocal distribution. Protocol preference varies with disease stage, patient clinical and laboratory conditions, and the degree of toxicity. Commonly used chemotherapy regimens include L-CHOP (vincristine, cyclophosphamide, doxorubicin, L-asparaginase, and prednisolone), CHOP, COP (cyclophosphamide, vincristine, and prednisone), LAP (lomustine, L-asparaginase, and prednisolone), LOPP (lomustine, vincristine, procarbazine, prednisolone), chlorambucil, and prednisolone. The prognosis of canine epitheliotropic cutaneous lymphoma is unfavorable, with a survival time ranging from a few months to 2 years. The animal in this study survived for 105 days. In addition, epitheliotropic cutaneous T cell lymphoma is aggressive, which may result in a shorter survival time in animals affected by this type of tumor. Keywords: epitheliotropic lymphoma, tumor, oncopathology, immunohistochemistry, mycosis fungoides