IMPORTANCE: Epithelioid sarcomalike (pseudomyogenic) hemangioendothelioma (ES-H) is a recently described and little-known vascular neoplasm that frequently presents with dermatologic lesions. Histopathologic characterization includes sheets or fascicles of plump, spindled and epithelioid, rhabdomyoblastlike neoplastic cells involving the dermis and often extending to subcutaneous tissue. Immunohistochemical analysis reveals neoplastic cells that show a constant immunophenotype characterized by immunoreactivity for cytokeratins and endothelial markers. OBSERVATIONS: We described the clinical, histopathologic, and immunohistochemical features of 2 cases of cutaneous ES-H. Clinical examination revealed multifocal lesions that consisted of erythematous nodules on the leg and foot in case 1 and small perioral papules in case 2. Neoplastic cells had a rhabdomyoblastic appearance, with large nuclei and ample eosinophilic cytoplasm. Immunohistochemical analysis revealed expression of cytokeratin AE1/AE3, CD31, ERG, and FLI-1, with focal and weak positivity for CAM 5.2 and smooth muscle actin. The nuclei of neoplastic cells showed intact expression of INI-1. This immunoprofile, especially the ERG positivity, demonstrated the endothelial nature of proliferating cells. CONCLUSIONS: We recommend adding the low-grade neoplasm ES-H to the large list of cutaneous vascular proliferations. Dermatologists should be aware of this low-grade cutaneous vascular tumor.
IMPORTANCE: Epithelioid sarcomalike (pseudomyogenic) hemangioendothelioma (ES-H) is a recently described and little-known vascular neoplasm that frequently presents with dermatologic lesions. Histopathologic characterization includes sheets or fascicles of plump, spindled and epithelioid, rhabdomyoblastlike neoplastic cells involving the dermis and often extending to subcutaneous tissue. Immunohistochemical analysis reveals neoplastic cells that show a constant immunophenotype characterized by immunoreactivity for cytokeratins and endothelial markers. OBSERVATIONS: We described the clinical, histopathologic, and immunohistochemical features of 2 cases of cutaneous ES-H. Clinical examination revealed multifocal lesions that consisted of erythematous nodules on the leg and foot in case 1 and small perioral papules in case 2. Neoplastic cells had a rhabdomyoblastic appearance, with large nuclei and ample eosinophilic cytoplasm. Immunohistochemical analysis revealed expression of cytokeratin AE1/AE3, CD31, ERG, and FLI-1, with focal and weak positivity for CAM 5.2 and smooth muscle actin. The nuclei of neoplastic cells showed intact expression of INI-1. This immunoprofile, especially the ERG positivity, demonstrated the endothelial nature of proliferating cells. CONCLUSIONS: We recommend adding the low-grade neoplasm ES-H to the large list of cutaneous vascular proliferations. Dermatologists should be aware of this low-grade cutaneous vascular tumor.