[A case of rectal GIST treated with imatinib mesylate neoadjuvant therapy to preserve the anus].

A 64-year-old man was admitted to our hospital with anal pain on evacuation. MRI revealed a large rectal submucosal tumor, more than 6 cm in diameter. Fine needle histological diagnosis indicated GIST with moderate risk. The patient was treated with imatinib mesylate in order to preserve the anus. The anal pain and tumor size decreased. Trans-anal local excision was performed. This case suggests that imatinib mesylate can make it possible to treat large rectal GIST cases by preserving anus, if neoadjuvant chemotherapy can be effective.