Systemic T cell large granular lymphocyte lymphoma with multifocal white matter degeneration in the brain of a Japanese domestic cat.

A 10-year-old spayed female Japanese domestic cat exhibited clinical symptoms suggesting pancreatitis. One month later the cat exhibited Horner's syndrome and was euthanized. At necropsy, multiple neoplastic masses were found in the intestines, spleen, kidneys, urinary bladder, and lungs. On cytology, many neoplastic lymphocytic cells had fine to large cytoplasmic granules, suggesting large granular lymphocyte (LGL) lymphoma. Histopathological examinations revealed infiltrative proliferation of the neoplastic cells in almost organs. Immunohistochemically, the neoplastic cells were intensely positive for CD3 and granzyme B. In the brain, there were multifocal white matter lesions characterized by diffuse myelin loss with mild infiltration of the neoplastic cells. Based on these findings, the cat was diagnosed as LGL lymphoma presumptively of intestinal origin with systemic involvement.