Parachordoma. A case report of a very rare soft tissue tumor.

An extremely rare and peculiar soft tissue tumor is described. Few examples of this tumor are classified under the term parachordoma, while probably many more are designated as chordoid sarcomas. The tumor presents histological features similar to those of chordoma, as well as to extraskeletal myxoid chondrosarcomas (chordoid sarcomas), and should also be differentiated from chondroid syringoma or mixed tumor of the skin. The tumor reported herein appeared as a deep cited soft tissue mass, presenting the histology of chordoma in an extra-axial localization. On the other hand, the positive immunoreactions of the tumor cells with cytokeratin and epithelial membrane antigen (EMA) ruled out the diagnosis of chondrosarcoma. It seems, therefore, that this is a special type of soft tissue tumor with bimodal differentiation (epithelial and mesenchymal) with good prognosis.