Malignant fibrous histiocytoma in dogs and cats.

Five soft tissue tumors of varied morphology in dogs and cats were classified as malignant fibrous histiocytomas on the basis of their histologic composition. All were composed of varying mixtures of histiocytes and fibroblasts and three contained large multinucleated cells. This giant cell variant of malignant fibrous histiocytoma was seen only in cats. These tumors are comparable to those described in man as malignant fibrous histiocytoma on the basis of the malignant histiocyte and its varied morphology and function.