Collagenous fibroma of the arm: a report of two cases

A recently proposed addition to fibrous tumors in soft tissue was first des cribed as desmoplastic fibroblastoma and later renamed collagenous fibroma. This tumor is clinically and morphologically distinct and benign. However, only a few series have been reported, and the clinicopathologic features a re not widely recognized. We present two cases of collagenous fibroma of th e arm. Both patients presented with an enlarging, well-circumscribed and mo bile soft tissue mass. Magnetic resonance imaging showed areas of low signa l intensity on both T1- and T2-weighted sequences, Needle aspiration cytolo gy revealed nondiagnostic samples because of the low cellularity of the tum ors. Each of the resected tumors was composed of low-cellular spindle- to s tellate-shaped cells in a fibrous matrix with clear margination. After the marginal excisions, no recurrences were observed. Clinicians should be awar e of this entity to prevent overtreatment, because imaging findings and cyt ologic features are similar to those of desmoid tumor.