Laparoscopic resection of a gastrointestinal stromal tumor of the rectum after treatment with imatinib mesylate: report of a case.

This report describes the laparoscopic resection of a rectal GIST after treatment with imatinib mesylate. A 56-year-old male presented with a submucosal tumor (longest diameter, 8 cm) arising in the lower rectum. A core needle biopsy revealed that the tumor contained bundles of spindle-like cells. Immunostaining revealed that the tumor was positive for c-kit and CD34. Analysis of the c-kit gene revealed a substitution of ACA (threonine) by GCA (alanine) at codon 574 of exon 11. Imatinib mesylate (400 mg/day) was given as preoperative adjuvant therapy for 3 months, and the tumor shrank to 5 cm in diameter. Proctectomy with transanal anastomosis could be performed laparoscopically, while preserving the anus. There was no evidence of recurrence 2 years 6 months after surgery. Preoperative adjuvant chemotherapy with imatinib mesylate may permit the use of less invasive treatment procedures, allowing anal preservation.