Abstract

Epithelioid angiosarcoma (EAS) is a highly aggressive and rare endothelial cell neoplasm. We present the first report of EAS demonstrating immunoreactivity with only one endothelial marker. The patient is a 53-year-old man status post heart transplant on immunosuppressive therapy, who presented with a 1.5 cm cutaneous nodule of the left lower leg that had been present for two years. The lesion was clinically favored to be a ganglion cyst and had recently become tender. A wide local excision was performed and histological examination revealed a tumor composed of sheets of malignant epithelioid cells with scattered mitotic figures. Immunohistochemical stains for squamous, soft tissue, and melanocytic differentiation were all negative. There was diffuse CD31 membranous positivity, while CD34, ERG, WT-1, and ETV4 were all negative. INI-1 was retained.  Despite the sole positivity of CD31, a diagnosis of EAS was rendered based on histomorphology and CD31 immunoreactivity. EAS typically presents as a nodule within the deep soft tissues.  Histologically, EAS is composed of sheets of cohesive epithelioid cells with minimal vascular formation. The poorly differentiated morphology in our case prompted a vast differential, which required an extensive immunohistochemical workup. To the best of our knowledge, all previously reported cases of EAS were diagnosed by a combination of at least two positive endothelial markers. Our case highlights the diagnostic challenge of EAS with an indolent clinical presentation and solitary CD31 immunoreactivity. The retained CD31 expression could be a potent target for systemic therapies particularly in chemotherapy-resistant advanced angiosarcomas.