Linfoma cutâneo e mucocutâneo epiteliotrópico de imunofenótipo T com apresentação incomum em cão

The aim of this report was to describe a clinical case of cutaneous and mucocutaneous epitheliotropic lymphoma with an atypical presentation pattern in an adult mixed-breed male dog. The patient presented with solitary and disseminated erythematous, ulcerated nodules in the inguinal, abdominal, and scrotal regions, along with involvement of mucocutaneous areas such as the perineal and labial regions. The disease showed rapid progression, with aggressive tumor growth, bloody discharge, ulceration, and intense pain. Biopsies of the lesions were obtained, and histopathological and immunohistochemical analyses confirmed a cutaneous and mucocutaneous epitheliotropic lymphoma of T-cell origin. Chemotherapy following the CHOP protocol—comprising cyclophosphamide, doxorubicin, vincristine, and prednisone, was initiated, together with clinical and medical supportive care. However, the patient died before the second chemotherapy session. Considering the rapid tumor progression, high neoplastic burden, and acute clinical deterioration after treatment initiation, tumor lysis syndrome was regarded as the most probable outcome. This syndrome results from massive destruction of neoplastic cells with the release of intracellular contents, leading to metabolic disturbances, renal injury, and systemic instability. It may occur spontaneously or following the onset of chemotherapy, as in this case. Although well documented in human medicine, tumor lysis syndrome remains poorly recognized in veterinary medicine, underscoring the importance of post-mortem examination. This case highlights the relevance of recognizing unusual clinical presentations of cutaneous and mucocutaneous epitheliotropic lymphoma for inclusion in the differential diagnosis.