Retrorectal tumors in adults: magnetic resonance imaging findings

To retrospectively evaluate the magnetic resonance imaging (MRI) features of adult retrorectal tumors and compare with histopathologic findings.

MRI features of 21 patients with preoperative suspicion of retrorectal tumors were analyzed based on the histopathological and clinical data.

Fourteen benign cystic lesions appeared hypointense on T1-weighted images, and hyperintense on T2-weighted images with regular peripheral rim. Epidermoid or dermoid cysts were unilocular, and tailgut cysts were multilocular. Presence of intracystic intermediate signal intensity was observed in one case of tailgut cyst with a component of adenocarcinoma. Six solid tumors were malignant lesions and showed heterogeneous intensity on MRI. Mucinous adenocarcinomas showed high signal intensity on T2-weighted and mesh-like enhancing areas on fat-suppressed T2-weighted images. There was a fistula between the mass and anus with an internal opening in mucinous adenocarcinomas arising from anal fistula. Gastrointestinal stromal tumors displayed low signal intensity on T1-weighted images, and intermediate to high signal intensity on T2-weighted images. Central necrosis could be seen as a high signal on T2-weighted images.

MRI is a helpful technique to define the extent of the retrorectal tumor and its relationship to the surrounding structures, and also to demonstrate possible complications so as to choose the best surgical approach.