To investigate the CT and MRI imaging features of aggressive angiomyxoma (AAM) and to provide evidence for differential diagnosis. To explore the important value of imaging examination in preoperative evaluation.

14 patients with pathologically confirmed AAM had CT and/or MRI examination. 14 patients underwent plain and contrast enhanced MRI of pelvic cavity and pelvic floor before operation. 8 patients underwent plain CT scan of abdominal and pelvic cavity. The imaging features, blood supply and the relationship with pelvic floor structure were observed. At the same time, perineal hernia caused by tumor was measured. Routine pathological examination was performed after operation.

(1) The masses were large, with a mean maximum diameter of (12.25±5.64) cm. (2) The lesions crossed the urogenital septum and pelvic septum and herniated into the perineal area in 10 cases (71.4%). (3) The lesions were hypodensity on the plain CT and hyperintense on T2WI. It was a characteristic sign of a lesion rich in mucinous matrix. The characteristic "swirled" or "layered" appearance was observed in T2WI and contrast enhanced T1WI. It is suggested that there are bundles of collagen fibers and vascular structures in the lesions. DWI and ADC images showed high signal, ADC value was (2.04±0.27)×10^-3 cm/s. It is suggested that there is no limited diffusion in the tumor.(4) The capsule was complete in 9 cases and incomplete in 5 cases. (5) The masses involved the pelvis, perineum and vulva, which were supplied by multiple arteries. The internal pudendal artery was the most common. The masses in vulva and inguinal area were mostly supplied by single artery.

AAM exhibits characteristic CT and MRI features. It can not only provide information in differential diagnosis, but also meticulously assess the blood supply of the tumor and its relationship with the surrounding tissues and organs, as well as provide accurate measurement for perineal hernia caused by the tumor, which can provide a basis for surgical plan selection.