Histopathological examination is required to confirm the diagnosis of retiform hemangioendothelioma (RH) because RH does not have distinctive clinical features. Histopathological examination reveals arborizing blood vessels in the dermis, extending between the collagen bundles in a reticular fashion and flanked by lymphocytes and hyaline sclerosis. The vessels are lined by monomorphic endothelial cells with scanty cytoplasm and prominent protuberance of the nucleus. The cells can protrude to the vascular lumen like a matchstick or hobnail, and nuclear atypia and mitotic figures are generally absent (Fig. 1).1 Some interspersed lymphocytes can also be seen in and around the blood vessels. Immunohistochemical examination of RH shows positive expression of vascular endothelial cell marker CD34 and weak positive expression of CD31 and FVIII-related antigen.2 This low-grade tumor recurs frequently, but the risk of metastasis is very low.
RH is an extremely rare variant of low-grade angiosarcoma that was first described in 1994 as a distinctive form of angiosarcoma.3 It often occurs in young or middle-aged people and has an unclear pathogenesis. Its main clinical feature is an asymptomatic, slowly growing, well-defined solitary nodular or plaque-like lesion on either the extremities or trunk (Fig. 2).2,4
The differential diagnoses for RH are angiosarcoma and targetoid hemosiderotic hemangioma. The histopathological features of angiosarcoma are very similar to those of RH. However, angiosarcoma often exhibits nuclear atypia and mitotic figures and the absence of a retiform pattern of blood vessels; additionally, it is more invasive than RH and has a higher risk of recurrence and metastasis. In contrast, targetoid hemosiderotic hemangioma is a superficial and limited lesion, and shoe nail-like vascular endothelial cells can only be seen in some areas.3 These lesions can be identified by histopathologic examination.
About 60% of patients with RH develop local recurrence with a tendency for local aggressive behavior. Previous reports have described regional lymph gland metastasis in a single patient and local spread to soft tissue in another patient.5 Only one RH-related death has been reported to date. Surgical excision is the most effective treatment for a circumscribed lesion.6
. Quadri S, Saeed N, Vasenwala SM, et al. Retiform hemangioendothelioma of the gluteal region: a case report. Saudi J Med Med Sci 2018;6(3):165–168. doi:10.4103/sjmms.sjmms_145_16.
. Rani S, Singh J, Ahuja AK, et al. Retiform hemangioendothelioma: a rare entity at atypical site. Indian J Dermatol Venereol Leprol 2016;82(5):550–552. doi:10.4103/0378-6323.183633.
. Zhang G, Lu Q, Yin H, et al. A case of retiform-hemangioendothelioma with unusual presentation and aggressive clinical features. Int J Clin Exp Pathol 2010;3(5):528–533.
. Ranga SM, Kuchangi NC, Shankar VS, et al. Retiform hemangioendothelioma: an uncommon pediatric vascular neoplasm. Indian J Dermatol 2014;59(6):633. doi:10.4103/0019-5154.143583.
. Mentzel T, Stengel B, Katenkamp D. Retiform hemangioendothelioma. Clinico-pathologic case report and discussion of the group of low malignancy vascular tumors. Pathologe 1997;18(5):390–394. doi:10.1007/s002920050231.
. Tamhankar AS, Vaidya A, Pai P. Retiform hemangioendothelioma over forehead: a rare tumor treated with chemoradiation and a review of literature. J Cancer Res Ther 2015;11(3):657. doi:10.4103/0973-1482.148693.