Three cases of collagenous fibroma with rim enhancement on postcontrast T1-weighted images with fat suppression.

Collagenous fibroma, also known as desmoplastic fibroblastoma, is a benign fibrous soft tissue tumor showing gradual growth, commonly without aggressive local infiltration. Today, preoperative radiological diagnosis is important to avoid over-treatment and unnecessary extensive procedures, but is difficult because diagnostic imaging findings for collagenous fibroma have not been established. We report MR imaging findings of three collagenous fibromas in correlation with their histopathology. The characteristic rim enhancement on post-contrast T1-weighted images with fat suppression was present in all three cases, and we consider this to represent the difference in vascularity between the outer capsule-like fibrous tissue and the inside of the tumor.