Gastrointestinal Stromal Tumor of the Anal Canal: A Rare Case Report and Literature Review

Abstract

Gastrointestinal stromal tumours (GISTs) are rare connective tissue tumours, accounting for only 1% of malignant tumours of the digestive tract, with a preferential location in the stomach (60%) and the small intestine (30%). Anorectal location is very rare and infrequently reported in the literature. GISTs are mesenchymal tumours that can occur in adults at any age, though they are rarely seen before 40 years old, with a peak incidence around 45-60 years and a gender ratio close to 1:1. Treatment is primarily surgical, sometimes combined with neo-adjuvant or adjuvant chemotherapy to improve resectability and reduce the potential for recurrence. The benefit of imatinib-based chemotherapy, which is an inhibitor of the transmembrane tyrosine kinase receptor (proto-oncogene), is clearly demonstrated in the management of stromal tumours, particularly those that are aggressive with a high grade of malignancy. A case of a stromal tumor in the anal canal was reported here. It was surgically treated by local excision, from the experience of the Medical-Surgical Proctology Department at Mohammed V Military Hospital in Rabat. Laboratory tests were within normal limits, with haemoglobin (Hb) at 13 g/dL, platelets (PLT) at 230,000/mm², prothrombin time (PT) at 90%, and normal tumour markers. The surgical treatment, performed under spinal anaesthesia with the patient in the lithotomy position, involved a vertical ischioanal incision, complete excision of the mass, and ensured clear surgical margins without capsular breach. The histopathological examination revealed an encapsulated lesion measuring 93 x 78 mm and weighing 110 grams. As Anorectal GISTs are rare, wide resection is generally recommended when the tumour is operable.