Pseudomyogenic hemangioendothelioma/epithelioid sarcoma-like hemangioendothelioma of the lower limb: report of a rare case (Diagnostic Pathology)

Pseudomyogenic hemangioendothelioma is an extremely rare soft tissue tumor, also named as epithelioid sarcoma-like hemangioendothelioma, which occurs more frequently in young adult males. It was originally recognized as a variant of epitheloid sarcoma, however it is now concluded as a distinctive, rarely metastasizing endothelial neoplasm. We present a case of pseudomyogenic hemangioendothelioma in the lower limb in a 49-year-old female who has a long course of disease and suffered from twice local recurrences and lymph node affection of the tumor. The mass was subcutaneous and the margins were ill-defined. Morphologically, the tumor cells show diversity, composed of large spindle cells and round cells, both with abundant eocinophilic cytoplasm, mimicking rhybdomyoplasts and epitheloid cells respectively. The tumor cells show diffuse strong expression of Factor VIII, Fli-1, INI-1, vimentin, MDM2, and CDK4, local expression of CD31, AE1/AE3, EMA and P63, and no expression of CD34, S-100, actin-sm, desmin, MyoD1, and HMB45. Based on these information, this case is diagnosed as pseudomyogenic hemangioendothelioma after ruling out the main differential diagnosises including epithelioid sarcoma, malignant peripheral nerve sheath tumor and rhabdomyosarcoma. From this case we suggest that pseudomyogenic hemangioendothelioma may be confused with a variety of soft tissue neoplasm histologically. The clinical feature of the case of a long course of disease with twice local recurrences and final lymph node involvement 10 years after excision of the primary tumor indicates a relative indolent behavior of this tumor.