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The Desmoid Tumor Research Foundation

October 2020

Adipocyte-rich CTNNB1-mutated Intramuscular Gardner Fibroma Progressing to Desmoid Fibromatosis

Author Information

Bakker A(1), Slack JC(1), Caragea M(1), Kurek KC(1,2), Brundler MA(1,3).

(1)Dept of Pathology and Laboratory Medicine, Cumming School of Medicine, Calgary, Alberta, Canada. (2)Dept of Genetics, Cumming School of Medicine, Calgary, Alberta, Canada (3)Dept of Paediatrics, Cumming School of Medicine, Calgary, Alberta, Canada.

Publication

Pediatr Dev Pathol

Summary

Herein, we report a unique case of an 11-year-old boy who presented with a rapidly growing soft-tissue mass after biopsy of a stable fat-rich lesion present in the calf muscles since infancy, with Magnetic resonance imaging findings suggesting an intramuscular adipocytic tumor. The resection showed gardner fibroma (GF) and desmoid fibromatosis (DF). DF arising from a preexisting GF (the so-called "GF-DF sequence") is a well-documented phenomenon. Although immunohistochemistry was negative for nuclear beta-catenin expression, a CTTNB1 S45F mutation, which has been associated with aggressive behavior in DF, was identified in both components using a next-generation sequencing-based molecular assay. This is the first time a mutation in CTNNB1 has been identified in GF and the GF-DF sequence, thus expanding our knowledge of the molecular pathogenesis of the GF-DF sequence and highlighting the role of molecular testing in pediatric soft-tissue tumors.

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