Immunohistochemical analysis of thymic carcinoma focusing on the possibility of molecular targeted and hormonal therapies.

ABSTRACT

OBJECTIVE: Thymic carcinoma is a rare mediastinal malignant tumor, and in many patients, the tumor is detected in an inoperable advanced stage. Even when chemotherapy is administered to such patients, the patients show a poor response. We investigated new biomarkers of therapeutic molecular targets. METHODS: This study included 44 patients diagnosed and treated for primary thymic epithelial tumors at Showa University Northern Yokohama Hospital, Showa University Hospital, and Showa University Fujigaoka Hospital from 2003 to 2011. We investigated new biomarkers of therapeutic molecular targets, such as the peroxisome proliferator-activated receptor γ (PPARγ), insulin-like growth factor 1 receptor (IGF1R), epidermal growth factor receptor (EGFR), estrogen receptor (ER), progesterone receptor (PgR), androgen receptor (AR), human epidermal growth factor type 2 (HER2)/neu, CD44, and L-type amino acid transporter 1 (LAT1), in thymic tumors. RESULT: Immunohistochemical analysis showed that the PPARγ positivity rate in thymic carcinoma was 32 %, which was significantly higher than that in thymoma (4 %). The IGF1R positivity rate in thymic carcinoma was 73 %, which was significantly higher than that in thymoma (27 %). CONCLUSION: Therefore, by examining the expressions of PPARγ and IGF1R, it would be possible to identify therapy-responsive patients and to improve results of thymic carcinoma treatment.