Wide local excision for anal GIST: A case report and review of literature

INTRODUCTION Gastrointestinal stromal tumors (GIST) are tumors of mesenchymal origin commonly detected in stomach and small bowel. GIST arising primarily from the anal canal is extremely rare. Due to the malignant potential, these tumors are treated with radical surgery like abdominoperineal resection. But with the advent of imatinib therapy and a better understanding of the tumor biology, some cases have been successfully treated with wide local excision. PRESENTATION OF CASE We describe a case of a 70-year-old lady presenting with a 2cm mass in the anal canal. Endoanal ultrasound revealed a well-circumscribed solid nodule in the intersphincteric space. The patient was successfully treated by wide local excision and adjuvant therapy with imatinib mesylate. DISCUSSION Only 14 confirmed cases of primary anal GIST have been reported in the literature. It appears as a well circumscribed hypoechoic mass arising from the intersphincteric space encroaching into the lumen on endorectal ultrasound. Lymphadenopathy is absent. Anal sphincters get involved as the lesion increases in size. Treatment is often planned based on the extent of the disease, the mitotic rate, patient's general condition and willingness for a permanent colostomy. CONCLUSION Small lesions (<2cm) with low mitotic rate may be successfully managed by local excision. Radical surgery should be reserved for large, aggressive tumors.