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

- Anal region is the primary site of origin in only 2% of all anorectal gastrointestinal stromal tumors (GIST) with only 14 cases reported in literature since 2000.
- Anal GIST appears as a well circumscribed hypoechoic mass arising from the intersphincteric space encroaching in to the lumen.
- Small lesions (< 2 cm) with low mitotic rate may be successfully managed by local excision.
- Radical surgery should be reserved for large, aggressive tumors.

IntroductionGastrointestinal 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 caseWe describe a case of a 70-year-old lady presenting with a 2 cm 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.DiscussionOnly 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.ConclusionSmall lesions (<2 cm) with low mitotic rate may be successfully managed by local excision. Radical surgery should be reserved for large, aggressive tumors.