Clear cell sarcoma of soft tissue in right parapharyngeal region: report of a rare case.

Clear cell sarcoma (CCS), initially named malignant melanoma of soft parts, is a rare malignant neoplasm typically involving deep soft tissue of the extremities, in close proximity to tendons and aponeuroses. Here we describe a case of clear cell sarcoma of the right parapharyngeal region in a young female aged 20 years. MRI detected a mass about 4.4 cm×3.4 cm×3.0 cm, located in the right parapharyngeal area and between the external pterygoid and the medial pterygoid. Microscopically, most of the tumor cells were epithelioid with palely eocinophilic cytoplasm arranged in sheets. Pleophorism of tumor cells were not marked. Immunohistochemical analysis shows that the tumor cells were positive for vimentin, S-100, HMB45 and MelanA, and negative for AE1/AE3, actin-sm, desmin, CD117, TFE-3, and P63. Ki67 index was about 5%.