Pseudomyogenic Hemangioendothelioma of Skin, Bone and Soft tissue - A Clinicopathological, Immunohistochemical and Fluorescence in situ hybridization study.

Pseudomyogenic hemangioendothelioma (PHE) is an uncommon neoplasm with propensity for local recurrence. The tumor mimics epithelioid hemangioendothelioma and epithelioid sarcoma, representing a possible diagnostic pitfall. We investigated the clinicopathological, immunohistochemical, and fluorescence in situ hybridization features of PHEs. Eight cases of PHE were retrieved from our pathology archives. The clinical and outcome information was available in 6 patients. In 6 cases, the tumors were located in the lower limb, whereas the upper limb was involved in 2 cases. Three patients had exclusively bone involvement, and 2 patients had cutaneous tumor only. The tumor was multifocal in 5 cases, of which 2 patients had simultaneous bone and soft tissue involvement. Immunohistochemical stains revealed all tumors to be positive for AE1/AE3 (8/8), ERG (7/7), and FLI-1 (7/7) with preserved INI1 (7/7) expression. Most of the tumors were variably positive for CD31 (7/8), CAM5.2 (2/3), and SMA (4/6). t(7;19)(q22;q13) fusion pattern was detected in 3 cases (5 tumors) with cutaneous and multifocal PHE. In 3 cases, a translocation pattern was detected in a few nuclei but did not meet our laboratory cutoff value. MYC amplification was not detected in any of the 5 cases examined, aiding in ruling out the possibility of angiosarcoma. Four patients underwent excision, and 2 with multifocal tumor required below-knee amputation. Six patients with outcome information were alive and free of disease after a median follow-up of 35 months. We conclude that ancillary techniques can be helpful in differentiating this unusual indolent tumor from potentially aggressive epithelioid hemangioendothelioma, epithelioid sarcoma, and epithelioid angiosarcoma. Long-term follow-up is warranted.