Curative resection for bulky rectal gastrointestinal stromal tumor after neoadjuvant imatinib mesylate

Gastrointestinal stromal tumor is the most common mesenchymal tumor of the gastrointestinal tract. However, the frequency of rectal gastrointestinal stromal tumor is relatively low. We described the case of a 54-year-old man with bulky rectal gastrointestinal stromal tumor of which a diameter was 10 cm. After eight-week neoadjuvant imatinib mesylate, the diameter of tumor was reduced to 6 cm. The patient did not have any distant metastases on preoperative computed tomography and magnetic resonance imaging. He underwent abdominoperineal resection. The radial margin was negative. Immunohistochemical staining showed that KIT and CD34 were positive. The number of mitosis was 13 per 50 high-power fields. Adjuvant imatinib mesylate was administered for one year. No recurrence was found for 43 months after a curative resection. Curative resection is the most promising treatment for gastrointestinal stromal tumor. However, neoadjuvant imatinib mesylate followed by surgical procedure seems to be one of the treatment options for locally advanced gastrointestinal stromal tumor.