Prolapsed giant rectal gastrointestinal stromal tumor presented with incarceration A rare case of emergency rectal lesion.

Prolapse of the tumor is an extremely rare clinical presentation in patients with rectal gastrointestinal stromal tumor (GIST). A 79-year-old male patient was consulted in the in-patient ward of internal medicine clinic of our hospital due to his incarcerated hemorrhagic mass protruding from the anal canal. Anal inspection revealed an incarcerated prolapsed hemorrhagic mass larger than 10 cm in diameter that looked like a cauliflower. The incarcerated rectal GIST protruding from the anal canal was removed by transanal excision under the emergency conditions. Clean surgical margins were obtained. No postoperative complications occurred. The histological diagnosis of high-risk GIST was made. Imatinib mesylate treatment was started postoperatively. The colorectum are the less common primary sites in adult GISTs (5%). Giant GISTs of the anorectum represent a real potential for anorectal emergency. They may be involved in rectal bleeding, obstruction, prolapse or incarceration. Prolapse of the tumor is an extremely rare clinical presentation in cases of rectal GISTs, and only a few cases have been reported in the medical literature so far. Complete surgical resection with en bloc excision of the tumor is the treatment of choice. Lower rectal GISTs are a rare entity that requires multidisciplinary management and long-term surveillance. We recommend, in case of lower rectal GIST, to perform an initial transanal local excision that achieves the essential R0 resection and define the risk of aggressive behavior and the involvement of the resection margins. Patients' close follow-up is mandatory to disclose as soon as possible local recurrences or metastases. Preoperative imatinib mesylate therapy and downstaging of the tumor may play an important role. KEY WORDS: Gastrointestinal stromal tumor, Incarceration, GIST, Prolapse, Transanal excision.