Aggressive large granular lymphocyte lymphomas in five dogs: a clinical cytohistological and immunological study

Among 276 canine lymphomas referred to the Haematology–Cytology–Immunology laboratory of the Lyon Veterinary School between 1997 and 2003, there were five aggressive large granular lymphocyte (LGL) malignancies. The five dogs were clinically examined and followed up. Cytological and histological analyses of the liver, spleen, lymph nodes, intestine and bone marrow were performed. The immunophenotype and proliferation index were established. The most significant clinical finding was that of an aggressive clinical course, the presence of hepatomegaly and/or splenomegaly, an abdominal lymphadenopathy, anaemia in four cases and blood and bone-marrow involvement in two cases. The cytological presentation was a diffuse infiltration of atypical, large granular lymphoid cells. Two cases were of the null type (CD3−, CD79a−, CD4−, CD8−), and three were of the T-cell type (CD3+, CD79a−, CD4−, CD8+). The proliferation index was high in all cases, with a median of 54.4%. The histological presentation of the null-type cases was an infiltration of the liver’s portal triads and the spleen’s red pulp. The T CD8+ cases showed two different patterns, characterised by infiltration: in the first, of all the intestine’s layers, the liver’s portal triads, the spleen’s red pulp and the lymph nodes and, in the second, infiltration of the liver’s sinusoids, the spleen’s red pulp. Although these aggressive LGL lymphomas are still poorly known, they may be compared to three types of human lymphoma: aggressive NK cell lymphoma/leukemia, hepatosplenic T-cell lymphoma and enteropathy-type T-cell lymphoma.