Lymphoma (malignant lymphoma, lymphosarcoma) in the dog

This report describes seven cases of canine lymphoma involving three German shepherd dogs, two boxers and two mongrels with a male to female ratio of 1–3 to 1. Their mean age and body weight was four years (range 1–5 to 8) and 31 kg (range 21 to 40), respectively. Six of the animals were euthanased at their owner's request and one died. Excessive lymph node enlargement, splenomegaly, hepatomegaly, blood lymphocytosis and proteinuria were the most striking clinical and clinicopathological findings. All the cases except one presented systemic signs and three developed secondary leukaemia because of bone marrow involvement. The anatomical types were classified according to the World Health Organization's criteria as thymic (one dog) and generalised (six dogs) and the clinical stage as IV (four dogs) and V (three dogs). Extranodal lymphomas involving the kidneys, meninges and the alimentary tract were seen in two cases. Histologically, the lymphomas were classified as lymphoblastic in four dogs, and in the remaining animals as lymphoblastic with plasmacytoid differentiation, lymphocytic with plasmacytoid differentiation, and poorly differentiated (stem cell) with one type appearing in each dog.