The pathology of spontaneously occurring malignant lymphoma in sheep.

The most common locations of tumours in 22 sheep with malignant lymphoma were the lymph nodes (19 sheep), spleen (14), liver (13), kidney (10), small intestine (9) and heart (9). The distribution of the lesions could be classified as multicentric (14 sheep, alimentary (6), skin (1) and thymic (1). Histological examination of malignant lymphomas from 40 sheep showed there were three reticulum cell sarcomas, and 37 lymphosarcomas. The lymphosarcomas were further classified on the basis of cytological features as lymphoblastoid, lymphocytic/prolymphocytic, prolymphocytic and lymphocytic in 14, 6, 11 and six cases, respectively. Viruses were not detected by electron microscopy in tumourous tissue from 10 sheep with malignant lymphoma.