Intestinal haemangiosarcoma in the cat: clinical and pathological features of four cases.

The clinical and pathological features of four cases of feline intestinal haemangiosarcoma are described. All cases were in domestic shorthaired cats and the mean age of the animals (n=3) was 13 years. The tumours originated in the colon, small intestine, ileocaecocolic junction or rectum. The rectal tumour was juxtaposed with an adjacent mast cell neoplasm. Metastasis to mesenteric lymph node occurred in two cases, and in one of these cats there was also abdominal seeding. The histopathological appearance was of a spindle cell neoplasm with vascular differentiation in each case. Immunohistochemical staining for factor VIII-related antigen, an endothelial cell marker, confirmed all four tumours to be of endothelial origin. The neoplastic endothelial cells lining irregular vascular channels were more likely to express the antigen than those forming denser sheets without obvious vascular differentiation.