Ovarian arteriovenous haemangioma in a female dog

Haemangioma is a vascular tumour, which occasionally may affect the ovary. Vascular tumours have to be differentiated by vascular abnormality (hamartoma) which closely resemble. Haemartoma is a congenital lesion but able to be very large in the adult due too its continuous growth. Haemangioma is a true vascular neoplasm which may involve and be responsive to therapy. The presence of normally organized arterioles or arteries and nervous structures in the lesional context may be indicative of a vascular hamartoma. A 12-year German shepherd bitch, with no heats in the previous two years, was admitted for abdominal distension and presence of a multicavitary structure of not-easily ultrasound evaluation. At laparotomy, the genital tract was removed including a large left ovarian neoplasm (31x20x7cm). The mass (weight 4 Kg) had a spongy and congested appearance and, at section, showed multiple cavitary blood filled structures. Uterus was congested and presented a severe endometrial cystic hyperplasia. The right ovary showed paraovarian cysts and an early granulosa cell tumour. Histologically the mass was characterized by newly-formed vessels, including small arterioles with a scant and abnormal elastic lamina, irregularly displaced into a fibromuscular stroma. No nerves were found inside the lesion by means of immunohistochemical search of S100 and PGP9.5 antigens. A diagnosis of arteriovenous haemangioma was made. The reported case showed the differential approach which allows to diagnose a haemangioma excluding a vascular hamartoma. The term arteriovenous haemangioma is used to underline the presence of neoplastic arterioles with a scant elastic lamina probably originated from veins.