Pseudomyogenic Hemangioendothelioma.

First described in 2003 as epithelioid-sarcoma-like hemangioendothelioma and later in 2011 as pseudomyogenic hemangioendothelioma, this rare vascular tumor is of intermediate malignant potential. It was officially included for the first time in the most recent World Health Organization's Classification of Tumours of Soft Tissue and Bone. It typically affects young adults with a predilection for the distal lower extremity. This tumor lacks morphologic features of vascular differentiation but shows unequivocal evidence of such differentiation with the use of relevant immunohistochemical stains such as FLI1, ERG, and CD31. Pseudomyogenic hemangioendothelioma can be diagnostically challenging and might be confused with other tumors, such as epithelioid sarcoma. In this review we discuss the clinical, morphologic, and immunohistochemical features of this tumor with particular emphasis on the differential diagnosis. Salient molecular and prognostic features are also reviewed.