Signet ring cell angiosarcoma: a hitherto unreported pitfall in the diagnosis of epithelioid cutaneous malignancies.

We report 2 cases of cutaneous epithelioid angiosarcoma featuring predominantly signet ring cells. The patients-a woman, 68 years of age, and a man, 85 years of age, respectively-were referred for slowly growing indurated plaques on their parietal and retroauricular skin. Microscopic examination showed diffuse dermal proliferations comprising polygonal cells and relatively abundant cytoplasm. Because the tumor cells often were distended by variably sized vacuoles pushing the nuclei to the periphery, the nuclear profile tended toward a crescent-like morphology. Abortive luminal formations were recognized. The tumor cells were positive for CD31, CD34, and D2-40/podoplanin, with no expression of epithelial or melanocytic markers. In 1 case, upon ultrastructural examination of paraffin-embedded tissue-cut from wax tissue and reprocessed-the optically empty spaces were surrounded by a membrane with ultrastructural features identical to those of the outer cell membrane, suggesting that these spaces corresponded to the formation of primitive intracytoplasmic lumina within the tumor cells. A few Weibel-Palade bodies also were noted. Our report offers further evidence that epithelioid angiosarcoma of the skin has a broad microscopic spectrum and that tumors displaying a preponderant population of signet ring cells pose further diagnostic challenges. A brief overview of cutaneous malignant tumors in the differential diagnosis of signet ring cell angiosarcoma is provided.