A rare case of multifocal pseudomyogenic hemangioendothelioma, involving soft tissues and bone, misdiagnosed as a rhabdomyosarcoma: Diagnostic and treatment implications.

Pseudomyogenic hemangioendothelioma (PHE) is an uncommon, but distinctive soft tissue tumor, characterized by multifocality. A 17-year-old male referred to us with progressively increasing multiple subcutaneous nodular lesions over his left leg and foot, reported elsewhere as a spindle cell rhabdomyosarcoma. On review, microscopy showed a cellular tumor comprising plump spindle cells arranged in loose fascicles with interspersed inflammatory cells. Tumor cells exhibited mild nuclear variation. Immunohistochemically, tumor cells expressed AE1/AE3, CD31, Fli-1, and smooth muscle actin (SMA), confirming diagnosis of PHE. Whole-body positron emission tomography-computed tomography (PET-CT) scan revealed multiple, metabolically active, subcutaneous nodular lesions over the left lower leg and in the distal tibia. Subsequently, resection specimens from the various lesions and bone curettage also revealed features of PHE. Three months later, the patient developed multiple lesions over his fourth toe and left foot, for which he underwent tumor resections. At present, he is disease-free. PHE is a locally aggressive soft tissue tumor characterized by multifocality, rarely bony involvement and can be misdiagnosed as a high-grade sarcoma.