[Epithelioid sarcoma with mesothelial and lymphatic endothelial differentiation: a clinicopathologic analysis of 10 cases].

To investigate the multidirectional differentiation potential in epithelioid sarcoma (ES), with special emphasis on its mesothelial and lymphatic endothelial markers expression. Ten cases of distal-type ES were included. The clinical, histological, and immunohistochemical(including mesothelial and lymphatic endothelial markers expression)features and follow-up data were evaluated. The patients aged between 8 to 66 years. Five cases were male and five were female. The tumors were located at the palm (2 cases), wrist (3 cases), upper arm (2 cases), poplitealfossa (1 case), lower leg (1 case) and thigh (1 case), respectively. Clinically, most cases presented as painful, firm subcutaneous nodules. Histologically, the tumors were mainly composed of epithelioid, rhabdoid, spindle, or transitional cells, with abundant eosinophilic cytoplasm, oval and vesicular nucleus, and one or more prominent nucleoli. They were arranged in nodular, diffuse nodular or sheet like growth patterns, frequently with necrosis at the center with vague granulomatous configuration. Immunohistochemically, all tumors expressed cytokeratins, epithelial membrane antigen, CD34, desmin, mesothelial markers such as Calretinin, WT1, D2-40, M2A, vascular and lymphatic endothelial markers FLI-1, and VEGFR-3. The tumor cells did not express CD31, FⅧRAg, HHF35, HMB45, Melan A, MyoD1, myogenin, S-100 protein and SMA. All 10 patients underwent radical resection or extended excision, with additional radiotherapy or chemotherapy. During the follow-up from October 2012 to August 2016, seven cases showed recurrences and metastases within 2 months to 2 years. Five patients died of the disease due to widespread metastases. ES may show a wide spectrum of morphology, and display a multidirectional differentiating capabilities including towards mesothelial and lymphatic endothelial cells. As such, its diagnosis and differential diagnosis are particularly important as it is easily confused with other tumors with similar morphology or immune phenotype.