Cutaneous haemangiosarcoma in a sheep: morphological, histopathological and immunohistochemical observations.

Haemangiosarcomas of animals are reported mainly in the dog and cat and less commonly in the cow, horse, pig and goat, but no cases have been reported in sheep. These tumours occur more commonly in internal sites than in the subcutis. A large mass in the right flank of a 6-year-old Sardinian sheep showed histopathological features of a haemangiosarcoma. The antibodies anti-Factor VIII-related antigen (FVIII-RAg) and anti-CD31 did not react immunohistochemically with either the normal or the neoplastic endothelial cells, whereas endothelin-1 strongly labelled both the normal and the neoplastic cells at different stages of differentiation. The results emphasize the usefulness of endothelin-1 as a vascular marker in sheep, particularly in the immunohistochemical detection of neoplastic endothelial cells.