Bovine Lymphosarcoma in California II. The Thymic Form

Abstract

Fourteen cases of bovine lymphosarcoma in which the primary lesion appeared to be in the thymus have been described. The animals were between 7 and 30 months of age and 10 were of the Hereford breed. Most of the lymphosarcoma cases encountered in Hereford cattle in California have been of this type, but there are insufficient epizootiological data to prove that this is a real, not an apparent, prevalence.Morphologically, the characteristic lesion was massive thymic enlargement. Apart from involvement of bone marrow and regional nodes, there were few lesions elsewhere in the body. Only one animal had a frank leukemia in spite of the frequent occurrence of bone marrow infiltration.Thymic lymphosarcoma generally differs from calf and adult forms of the disease with respect to age of the affected animal and characteristic morphological features.