Erythrophagocytic low-grade extranodal T-cell lymphoma in a cat

A 13-year-old male castrated domestic shorthair cat was presented to the referring veterinarian with a 2-month history of weight loss and lethargy. Splenomegaly, hepatomegaly, nonregenerative anemia, neutropenia, and hyperbilirubinemia were noted. Results of testing for feline immunodeficiency virus, feline leukemia virus, Toxoplasma gondii, and Mycoplasma sp. were negative. On cytologic examination of aspirates from the enlarged spleen and liver, a population of erythrophagocytic round cells was observed. Splenectomy and a liver biopsy were done which revealed a population of CD3+/CD79a- erythrophagocytic mononuclear round cells localized in the hepatic and splenic sinusoids. T-cell PARR (PCR for antigen receptor gene rearrangements) analysis of bone marrow and spleen demonstrated a single band indicative of a clonal proliferation of T cells. Based on the marked splenomegaly, sinusoidal infiltration, lack of lymphadenopathy, and results of cytology, PARR, and immunophenotyping, a diagnosis of low-grade extranodal T-cell lymphoma was made. The cat was treated with chlorambucil and prednisolone; clinical and laboratory abnormalities resolved and the cat has remained clinically normal for 2.5 years. To our knowledge, this report documents the first case of an erythrophagocytic T-cell lymphoma in a cat. The clinicopathologic findings were suggestive of hepatosplenic T-cell lymphoma, a neoplasm described previously only in humans and dogs.