Imatinib therapy for a patient with metastasis of colonic gastrointestinal stromal tumor: report of a case

Gastrointestinal stromal tumors (GISTs) developing in the colon are rare, accounting for <5 % of all GISTs. There are few data on the clinical efficacy of tyrosine kinase inhibitors in colonic GISTs. We report here on an 80-year-old male patient with advanced GIST of the transverse colon. The patient underwent palliative resection of the primary tumor because the disease was associated with multiple liver metastases and peritoneal dissemination. Immunohistochemical analysis of the surgical specimens showed KIT and CD34 expression. Sequence analysis revealed that the tumor harbored deletion mutation at codons 557-558 in exon 11 of the c-kit gene. A diagnosis of colonic GIST was made. The patient postoperatively underwent imatinib therapy for the remaining metastatic tumors. Imatinib therapy induced a cyst-like appearance of the liver metastases and stabilized the disease. In the present case, c-kit gene analysis was found to be clinically helpful for validating the diagnosis and therapeutic decision making for this rare disease.