Malignant neoplasm of mixed mesenchymal and neuroepithelial origin (ectomesenchymoma) of thigh.

A 49-year-old man had a malignant soft tissue tumor of the right thigh with metastasis to the femoral region and lower quadrant of the anterior abdominal wall on the right side and the left supraclavicular lymph nodes. The neoplasm showed features of chondrosarcoma and primitive neuroectodermal tumor (combined neuroblastoma, ependymoma, astrocytoma, and oligodendroglioma). The gliomatous part of the mixed tumor was confirmed by identification of the glial fibrillary acidic protein (GFAP). The diverse cellular population suggests a tumor origin from the ectomesenchymal remnant of the neural crest. The mesenchymal component of the neural crest would differentiate into the chondrosarcoma and the neuroectodermal component into the primitive neuroectodermal neoplasm. These various neoplastic elements, then, would form a neoplasm of mixed mesenchymal and neuroepithelial origin or an ectomesenchymoma.