Thymic Carcinoma with Overexpression of Mutated KIT and the Response to Imatinib

To the Editor: In April 2002, a 54-year-old man presented with thoracic pain and respiratory distress; a mediastinal mass, 7.7 by 6 cm, was found on positron-emission tomographic and computed tomographic scanning. Further examination showed elevated liver-enzyme levels and multiple liver metastases. Liver biopsy revealed metastatic, poorly differentiated epidermoid carcinoma of the thymus, 1 with strong KIT expression (Figure 1). The patient started taking imatinib at a dose recommended for the treatment of gastrointestinal stromal tumors (400 mg per day). 2 Within one week, his pain and respiratory distress disappeared. His liver metastases shrank within four months, and his liver-enzyme levels normalized, . . .