Sezary syndrome in a dog

Abstract

Sezary syndrome was diagnosed in a dog with epidermotropic lymphosarcoma and a leukaemic blood picture wherein 73.5% of the leucocytes (15582 of 21200 leucocytes /µl of blood) were large mononuclear cells with markedly convoluted nuclei. The dog had a history of multiple skin tumours progressing to hepatosplenomegaly and lymphadenopathy. Alpha-naphthyl acetate esterase staining of blood smears and splenic imprints revealed a focal to multifocal pattern of cytoplasmic enzyme activity that resisted sodium fluoride inibition, indicating that the neoplastic mononuclear cells were T lymphocytes. The neoplastic cells were negative for Sudan black B staining, myeloperoxidase activity, and chloroacetate esterase activity. Ultrastructurally, these cells had convoluted to cerebriform nuclei, 1 to 2 nucleoli, scattered mitochondria, numerous free ribosomes, and a few profiles of rough endoplasmic reticulum. Histological study of tissues collected at necropsy revealed infiltration of the skin, lymph nodes, spleen, liver, and bone marrow with neoplastic lymphocytes.