Unusual Neuroendocrine Differentiation in a Small Round Cell Angiosarcoma: A Potential Histologic Mimicker of Superficial Ewing Sarcoma.

Neuroendocrine differentiation or aberrant expression of neuroendocrine markers is very uncommon in angiosarcomas (AS) and creates a challenging differential diagnosis with other superficial or soft tissue tumors. Herein, we report a new case of superficial AS presenting as a tumor lesion on the little finger of the right hand of a 52-year-old man. The tumor displayed CD56, chromogranin-A, and synaptophysin immunoreactivity. Tumor cells were positive for vascular markers (CD31, FLI1, ERG, D2-40, VE-cadherin, VEGR1,2, and 3), CD99, and EMA, but were negative for S100, CK (AE1/AE3), CK20, polyomavirus, and myogenic (desmin and myogenin) and melanocyte markers (melan-A and HMB45). Ki67 immunos…