Collagenous fibroma (desmoplastic fibroblastoma) is a benign fibrous soft tissue tumor that usually occurs in the subcutaneous tissue or skeletal muscle of adults. Recent cytogenetic studies have revealed clonal rearrangements of the chromosomal band 11q12. We present a unique case of collagenous fibroma arising in the right shoulder of a 63-year-old female. Magnetic resonance imaging showed a solid soft tissue mass deeply relative to the deltoid muscle, with low-to-intermediate signal intensity on T1-weighted sequences and low-to-slightly high signal intensity on T2-weighted sequences. Contrast-enhanced fat-suppressed T1-weighted sequences demonstrated heterogenous internal enhancement with rim enhancement. Following an open biopsy, marginal excision of the tumor was performed. Histological examination confirmed the diagnosis of collagenous fibroma. Cytogenetic analysis displayed a simple karyotypic change with trisomy 8. The postoperative course was uneventful, and the patient is doing well without local recurrence two months after the surgery. To the best of our knowledge, this is the first case of collagenous fibroma with trisomy 8 as the sole cytogenetic abnormality.
Keywords: Collagenous fibroma; cytogenetics; desmoplastic fibroblastoma; magnetic resonance imaging; trisomy 8.