Giant gastrointestinal stromal tumor of the vermiform appendix: A case report.

Gastrointestinal stromal tumors (GISTs) of the vermiform appendix are rare, measuring <3 cm in 82.4% of the reported cases. Neoadjuvant therapy with the receptor tyrosine kinase inhibitor imatinib mesylate has the potential to improve resectability and organ preservation rates in locally advanced or metastatic/recurrent GISTs. We herein report the case of a 67-year-old male patient with an unusually large GIST (22 cm in diameter) of uncertain origin in the right lower abdominal quadrant, with a solitary peritoneal metastasis. Due to the size of this GIST and presence of metastatic disease, neoadjuvant therapy with imatinib (400 mg/day orally) was administered. Follow-up imaging studies revealed marked shrinkage of the primary and metastatic tumors. Subsequently, laparoscopic exploration revealed that the main tumor originated from the tip of the vermiform appendix, and that the peritoneal metastasis was located in the ascending mesocolon. The patient underwent laparoscopic appendectomy and excision of the peritoneal metastasis, without tumor rupture. Therefore, in appropriately selected patients, neoadjuvant imatinib for borderline resectable or oligometastatic GISTs may be a reasonable choice.