Intravascular papillary endothelial hyperplasia of the conjunctiva in a horse.

OBJECTIVE Vascular tumors of the conjunctiva in the horse are rare. We present a unique case of an intravascular papillary endothelial hyperplasia of the conjunctiva. ANIMAL STUDIED Horse. PROCEDURES Case report. A 6-year-old-mare presented with a red mass in the conjunctiva of the left eye. After complete ophthalmologic examination the lesion was excised. The tissue was processed for light microscopy and studied histopathologically. RESULTS Pathologic examination revealed a nonencapsulated vascular lesion composed of confluent vascular spaces filled by multiple papillary structures composed of a central collagenous core lined by hyperplastic endothelial cells. There was neither atypical endothelial cell nor mitotic activity. CONCLUSIONS Intravascular papillary endothelial hyperplasia is a benign proliferative lesion that should be differentiated from malignant vascular tumors.