Extra‐nodal T‐cell lymphoma infiltrating the anus, liver, mammary gland, ovaries and vulva of a French bulldog

Abstract Lymphoma infiltration into the reproductive system is rare, especially in young dogs. This case describes a 4‐year‐old, entire French bulldog with T‐cell lymphoma. The dog presented with mammary nodules, generalised mammary development, enlarged pre‐scapular lymph nodes, an anal nodule, and a large, ulcerated vulval mass. Further investigations demonstrated pleural effusion, hepatomegaly, renal abnormalities, ovarian enlargement, uterine distension and iliac lymphadenopathy. Histopathology identified neoplastic round cells infiltrating multiple sites, consistent with epitheliotropic lymphoma. Immunohistochemistry confirmed T‐cell lymphoma and highlighted tropism for mammary epithelium lining acini and ducts. Despite supportive care, the patient's condition worsened, and chemotherapy was declined, leading to euthanasia. This is the first documented case of canine lymphoma extensively affecting the reproductive system, including the ovaries, vulva and mammary glands, and the first report of T‐cell canine lymphoma infiltrating the mammary gland. This case highlights the need to consider lymphoma as a differential diagnosis for canine reproductive system neoplasia.