Neoadjuvant imatinib in a gastrointestinal stromal tumor of the rectum: report of a case.

Gastrointestinal stromal tumors (GISTs) are rare tumors of the gastrointestinal tract, and of these, GISTs involving the rectum are uncommon. This report describes a case of effective neoadjuvant therapy for a rectal GIST expressing the c-kit gene, where a laparoscopic ultralow anterior resection was successfully performed, thus preserving the anus. A 57-year-old woman visited our hospital due to constipation and was found by a digital examination to have a soft mass on the right wall of the rectum. Computed tomography revealed an 8.0 x 5.0-cm mass with an unclear margin adjacent to the rectum. A biopsy specimen was positive for CD34 and the c-kit gene product, but it was not positive for smooth muscle actin or S-100 protein, and thus the tumor was diagnosed as GIST. An abdominoperineal resection is generally essential for large rectal GISTs; however, she refused this operation. Neoadjuvant treatment with Imatinib decreased the tumor size (4.0 x 3.5 cm) and the anus was preserved by a laparoscopic ultralow anterior resection with direct coloanal anastomosis. She had no evidence of disease for 24 months postoperatively. To preserve the anus, a rectal GIST expressing the c-kit gene is best treated with Imatinib as neoadjuvant therapy.