A Rare Case of Multiple Gastrointestinal Stromal Tumors Coexisting with a Rectal Adenocarcinoma in a Patient with Attenuated Familial Adenomatous Polyposis Syndrome and a Mini Review of the Literature.

Background: Multiple gastrointestinal stromal tumors (GISTs) are extremely rare entities that exist either as spontaneous GISTs or as part of various syndromes, such as Carney's triad and type I neurofibromatosis (NF1). Attenuated familial adenomatous polyposis (AFAP) is a variant of familial adenomatous polyposis (FAP) with a milder clinical presentation. Both GISTs and AFAP have been reported to coexist with colorectal cancer, but the coexistence of GISTs and AFAP has never been reported in the literature before.

Case Report: A 45-year-old male patient with known AFAP arrived scheduled for a total colectomy and ileo-rectal anastomosis due to the malignancy of one of the previously biopsied polyps of the upper rectum. Intraoperatively, multiple nodular tumors were found at the jejunum within a length of 45 cm, for which an enterectomy and enteroanastomosis were performed. A histopathological examination of the whole colectomy specimen confirmed the presence of multiple polyps in the large intestine along with a rectal invasive adenocarcinoma. At the same time, in the examined part of the small intestine, 15 GISTs sized from 0.5 to 2.0 cm of prognostic group I, were identified. The patient's postoperative course was uncomplicated.

Conclusion: Multiple GISTs may present as an asymptomatic disease, and the same thing is true for colorectal cancer. Therefore, the appropriate screening is crucial for entities such as AFAP, since the surgery was performed because of the malignant transformation in one of the polyps and revealed multiple GISTs, as well.