Histologic and Immunohistochemical Characterization of Hemangiomas in the Skin of Seven Young Horses

Abstract

Abstract. The histologic and immunochemical characteristics of benign vascular tumors excised from the skin of seven young horses were evaluated. The patients were male horses of various breeds and were 16 months of age or younger at the time of presentation. Six tumors occurred on the extremities, and one was removed from the lip. Histologically, most tumors consisted of cellular nodules of varying compactness with few to many blood-filled lumina. Nodular growth separated preexisting adnexa and subcutaneous collagen. Some tumors contained or consisted predominantly of loosely packed arrays of ramifying arteries, veins, and capillaries separated by collagen within the dermis and subcutis. Within areas of nodular growth, multilayered vascular walls were encircled by reticulin strands that surrounded the endothelium and adjacent pericytes and also separated nonperivascular cells in the mass. Immunohistochemical staining of factor-VIII-related antigen and labeling by Ulex europeus-1 lectin was restricted to an innermost layer of cells surrounding vascular spaces, confirming their vascular endothelial origin. The plump fusiform cells arranged concentrically around the endothelium and some of those unassociated with vascular lumina stained with antibody to a-smooth muscle actin, as did the muscularis of larger vessels inside and outside of tumor nodules. These findings demonstrate an orderly arrangement between endothelium and supportive cells in these benign vascular neoplasms of young horses, similar to that observed during vascular development.

Clinicopathological Features of Hemangioma in Two Young Horses

“…This neoplasm has been reported mainly in the skin of limbs, with a multifocal growing pattern [7], which is in agreement with the two reported cases. Some authors reported the invasion of adjacent structures such as tendon and synovial sheath [3,8].…”

“…The wall of larger proliferated vessels also presented muscle actin-and desmin-positive spindle cells resembling pericytes/smooth muscle cells. This pattern was reported in 7 of 9 cutaneous hemangiomas in young horses [7].…”

Congenital tumours and tumour‐like lesions in domestic animals. 3. Horses. A review

“…This form may occur in an enzootic form (5 (18,42) or not recognized (56). It is conceivable however, that papillomavirus might occasionally exist in a latent form in utero and becomes manifest when fetal skin attains a critical level of maturation (56 (23,28,29,69). The fact that most cases occurred in horses that were less than one year old and that at least 11 foals (table 2) An interesting lesion was reported to occur in a newborn filly (54).…”

Intrapelvic Hemangiosarcoma in a Horse

“…8,11,13 Positive staining for factor VIII-related antigen was strongest in nonneoplastic endothelial cells of small capillaries, arterioles, and veins (Fig. 5).…”