Hemangioma of the Conjunctiva
Definition: Proliferation of blood vessels within the substantia propria.
Incidence/ Prevalence: 3 cases of conjunctival hemangioma were reported from a series of 632 conjunctival biopsies, over 25 years so it is extremely rare in pathology material.
Etiology: Some consider the hemangioma of the conjunctiva as a benign neoplasm whereas others consider it an overgrowth of mature tissue that exist normally in the conjunctiva. In the latter instance it would then be considered the most common variety of hamartoma in the conjunctiva.
Clinical Findings: Although it may involve only the conjunctiva, typically the hemangioma is also present in the eyelid, face, and orbit. 
In the image shown the lesion involves the bulbar conjunctiva, plica and the caruncle. Congenital hemangiomas are detected at or shortly after birth as elevated, soft, red-purple nodules that may continue to grow in the first year of life before stabilizing. The majority of cases then begin a slow process of involution, resulting in complete regression.
Histopathology: The pathologic findings of conjunctival hemangioma change with age. In the early life of the lesion, biopsies reveal a cellular proliferation of plump endothelial cells forming solid nests and cords within the connective tissue stroma. Mitotic figures are often present. In more mature hemangiomas the endothelial cells flatten, forming easily recognizable capillary lumina.
The image above shows large thinned walled vessels filled with blood (arrow 1). In addition erythrocytes have extravasated from the vessels (arrow 2) that are lined by a single layer of endothelium (arrow 3). Click on the image to enlarge it. In the trichrome stained section below of the same case, small capillary size vessels are evident (arrow 4). In addition there are slightly larger vessels (arrow 5). The walls of the vessels contain only a thin layer of collagenous material (blue) (arrow 6). In the involutional phase the lobules of capillary proliferation are replaced by fibrous tissue. 
Treatment: Removal is rarely needed and is indicated if vision is compromised. Conjunctival hemangiomas are known to involute without treatment.
