Pulmonary Metastasis after Resection for Gastrointestinal Stromal Tumor in the Rectum

A 71-year-old woman who had received resection for gastrointestinal stromal tumor (GIST) in the rectum after imatinib mesylate administration, revealed a pulmonary nodule measuring 11 × 10 mm in the right lung on chest computed tomography (CT), which was 26 months after the operation. The pulmonary nodule had gradually increased to 13 × 13 mm in diameter on follow-up chest CT. The standardized uptake value (SUV) of the pulmonary nodule on positron emission tomogram (PET) with 2-fluoro-2-deoxy-D-glucose (FDG) was 1.8. For diagnostic and therapeutic purposes, thoracoscopic partial resection of the lung, including the nodule, was performed. The pathological findings showed pulmonary metastasis from rectal GIST. On immunohistochemical examination, the tumor was diagnosed as the high-risk group, whereas the primary site in the rectum was the lowrisk group according to the Modified Fletcher classification. Imatinib mesylate was administered again, but her disease progressed. Although pulmonary metastasis from rectal GIST is a rare disease with a possible poor prognosis, pathological diagnosis should be essential to deciding treatment modality.