A Rare Case of Vascular Proliferation in the Mandible of a Juvenile Horse

Abstract

A fast growing, circumscribed, unilateral swelling of the right mandible of a juvenile horse was observed. Within few weeks, the continuously growing mass reached dimensions ranging from 7 to 10 cm in diameter and resulted in loss of the first deciduous premolar of the affected side. The animal was euthanized due to lesion progression. Histologically the mandibular swelling consisted of numerous variably sized vascular structures, partly filled with erythrocytes and embedded in a loosely arranged fibrous stroma within the medullary cavity of the mandible. Juvenile mandibular angiomatosis was diagnosed. To the authors' knowledge this is the first description of this rare entity in the mandible of a foal.

Keywords: angiomatosis; congenital; equine; horse; mandibular mass; vascular proliferation.

Figure 1

Swelling on the right mandible (A; white star) of a foal, showing extensive growth and consecutive loss of the first deciduous premolar (B). The cut surface was reddish and of gelatinous consistency (C). Transverse CT image of the oral mass involving the right mandible (D; arrow).

Figure 2

Histochemically and immunohistochemically, the swelling was composed of a dense meshwork of vascular structures of variable calibers partly divided by collagenous fibers (A; inset shows a representative section in Heidenhains's trichrome stain). Predominantly thin-walled, venous vessels (arrowheads) and fewer small capillary structures (stars) with single interspersed thick-walled, arterial vessels (arrow) could be detected within a slightly mucinous stroma (B; inset shows a representative section in alcian blue stain). Vascular walls stained highly positive for factor VIII-related antigen (C) as well as for CD31 (D), indicating a proliferation of blood vessels.