Congenital Ovarian Vascular Hamartoma in a Horse

An incidental finding in a 2-day-old female Quarterhorse that died of apparent septicemia was a 4 x 6 cm dark red, indurated, ovoid mass attached by a short stalk to the left ovary (fig.1).Cut surfaces showed solid to slightly cavernous tissue which oozed dark red blood when compressed.Light microscopy showed vascular channels lined by mature endothelial cells and separated by abundant connective tissue stroma (fig.2).Vascular disruption with acute hemorrhage and rare hemosiderin-engorged macrophages occurred throughout the sections.The mass had a thin, irregular cover of dense connective tissue continuous with the vascular stalk.The gross and histologic findings were consistent with congenital ovarian vascular hamartoma.Ovarian vascular hamartomas have been reported in the cow and sow [ 1,2,3].There are no previous reports of a hamartoma in the horse.