Focal epithelioid features are common in conventional angiosarcomas. Epithelioid angiosarcomas are exclusively composed of epithelioid tumors cells. The anatomic distribution is wide and includes skin, soft tissues, and internal organs. Cases have been reported in association with foreign bodies, radiation therapy, and arteriovenous fistulas.
The tumors are usually solitary and composed of solid sheets of large epithelioid cells with abundant eosinophilic or amphophilic cytoplasm, vesicular nuclei, and prominent nucleoli. Increased mitotic activity, hemorrhage, and necrosis are commonly present. Usually, there is no prominent vessel formation, although a few intracytoplasmic lumina with red blood cells may be seen.
Immunostains for CD31 and FLI-1 are positive. Cytokeratin and EMA are positive in 50% and 25% of cases respectively.
Epithelioid angiosarcomas are often mistaken for carcinomas or melanocytic neoplasms as there are infrequent or no vascular lumina. The differential diagnosis includes metastatic carcinoma, melanoma, epithelioid sarcoma and epithelioid malignant peripheral nerve sheath tumor. All of these entities lack intracytoplasmic vascular lumina (or formation of anastomosing vascular channels) and are negative for endothelial markers (CD31, FLI-1). The prognosis is poor with early metastasis and high mortality.