Pathologic complete response confirmed by surgical resection for liver metastases of gastrointestinal stromal tumor after treatment with imatinib mesylate.

A 39-year-old male underwent distal gastrectomy for a high grade gastrointestinal stromal tumor (GIST). Computed tomography (CT) and magnetic resonance imaging (MRI) 107 mo after the operation, revealed a cystic mass (14 cm in diameter) and a solid mass (9 cm in diameter) in the right and left lobes of the liver, respectively. A biopsy specimen of the solid mass showed a liver metastasis of GIST. The patient received imatinib mesylate (IM) treatment, 400 mg/day orally. Following the IM treatment for a period of 35 mo, the patient underwent partial hepatectomy (S4 + S5). The effect of IM on the metastatic lesions was interpreted as pathologic complete response (CR). Pathologically verified cases showing therapeutic efficacy of IM have been rarely reported.