Presumptive primary central nervous system T cell lymphoma in a deer (Capreolus capreolus)

This report describes the morphological and immunohistochemical findings in an approximately 7-year old wild European roe deer (Capreolus capreolus) with an infiltrative primary central nervous system T cell lymphoma. The roebuck had lost its timidity and was shot by a hunter. It was submitted for necropsy to exclude rabies. Gross examination revealed besides a verminous pneumonia no abnormal findings. Histologically, there was a highly cellular, not well demarcated, unencapsulated, and infiltrative neoplasm within basal parts of the brain. Tumour cells were round, up to 15 μm in diameter and loosely arranged in sheets with a multifocally predominant perivascular infiltration. Immunohistochemically, tumour cells were positive for CD3 antigen. Whilst secondary lymphomas of the central nervous system emerge by metastatic seeding of tumour cells, primary lymphomas originate within the neuroparenchyma. This is the first report of a primary central nervous system lymphoma in an European roe deer.