Immunohistochemical and molecular genetic analyses of multiple sporadic gastrointestinal stromal tumors

A 77-year-old Japanese male patient was admitted to our hospital complaining of general fatigue and melena. A gastroduodenal endoscopic examination revealed no definitive localized lesions. However, both a large amount of cruor and blood flow from the small intestine into the ascending colon was observed during the colonoscopic examination. At least three tumors, believed to originate from the small intestine, were detected by abdominal computed tomography. Based on these findings, multiple and hemorrhagic small intestinal tumors were diagnosed and surgical treatment of the tumors planned. During the celiotomy, twelve tumors were found in the small intestine. Intestinal wedge or partial resection was applied. All excised specimens demonstrated morphology of a submucosal tumor and the largest tumor had a delle with coagulation on the mucosal face. In the histological findings, hematoxylin and eosin staining showed spindle cell morphology. The immunohistochemical examination revealed that the tumor cells were diffusely positive for KIT and CD34. The myenteric plexus layer of the small intestine was focal-positive for KIT and showed no intestinal cells of Cajal hyperplasia. The tumor sequencing results revealed an identical missense mutation in codon 642 of c-kit exon 13 leading to the replacement of lysine by glutamic acid and a silent germ-line mutation in exon 12 of the PDGFRA gene concerning whole blood, normal mucosa and tumors. We concluded that the current subject was categorized as having multiple sporadic-type gastrointestinal stromal tumor with identical mutational types. Although the patient did not receive any adjuvant chemotherapy, there has been no sign of recurrence over the 3 years since the surgery.