CT and MRI features of aggressive angiomyxoma

Objective To analyze the imaging features of aggressive angiomyxoma (AAM) on CT and MRI. Methods Seven patients with pathologically confirmed AAM had CT and/or MRI examination within 1 week prior to surgery. Six patients had multi-slice helical CT scanning while four of the six patients had multi-phase contrast enhancement. Five patients had MR scanning with contrast administration covering the chest, mid-abdomen or pelvis. The imaging and pathological findings were retrospectively reviewed. Results (1) CT presentations: pre-contrast CT images revealed isodensity (1 case), heterogeneous density (5 cases), cystic degeneration (2 cases) and mural nodule (2 cases). Contrast CT images showed homogeneous and gradual enhancement (1 case), heterogeneous and progressive enhancement (3 cases), whorl sign (3 cases) and opacification of small vessels (3 cases). (2) On MR images, five cases showed high or slightly high signal on T2WI; three cases presented with whorl sign; two cases had cystic degenerations. Iso-signal or low-signal was shown at T1WI in all five cases. DWI demonstrated high or mildly high signal in five cases. At contrast images, a whole-lesion homogeneous and gradual enhancement was present in one case. Four cases revealed progressive and expanding enhancement, where whorl sign and gradual enhancement were present in three cases. A progressive ascending pattern of time-signal curve was delineated in three cases. (3) Microscopically, the tumor comprises of poorly-defined satellite or spindle cells with sparse cytoplasm and varied sizes of vessels, which distribute among stroma with rich collagen fibre and myxoid. Those components were heterogeneous to congregate compact cell cluster. The stroma in four cases was abundant in collagen fibre that was aligned with myxoid stroma and tumor cell alternately. Conclusion AAM exhibits characteristic CT and MRI features. The imaging features correlated well with pathological findings. Key words: Myxoma; Tomography,X-ray computed; Magnetic resonance imaging; Pathology