Expression of MET in alveolar soft part sarcoma.

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma which is characterized by the presence of a specific chromosomal translocation encoding the chimeric transcription factor (ASPL-TFE3) that activates expression of MET. We reviewed the clinical features and treatment outcome of 12 ASPS patients. The presence of ASPL-TFE3 fusion transcripts was assessed by reverse transcriptase polymerase chain reaction. In addition, we performed immunohistochemical studies for MET, TFE3, Ki-67, and EGFR expression. Lower extremity was the most commonly affected primary site (2 thigh, 3 lower leg, and 1 foot). Of four patients who received primary cytotoxic chemotherapy, no patient demonstrated treatment response. With follow-up duration of 94.4 months, median overall survival was 53.2 (95% C.I. 40.9-65.5) months. The immunohistochemical staining demonstrated 100% TFE3 positivity (8 of 8), 75% MET positivity (6 of 8) with a strong association between TFE3 expression and MET positivity with correlation coefficient of 0.808 (P = 0.02). The high expression of MET in ASPL-TFE3 (+) ASPS may further support the potential role of targeted agents against MET in this rare, chemoresistant tumor.