Beta-catenin is a 92 kD protein that is often present in thesub membranous region of the cell’s cytoplasm. Thisprotein accumulates in the nucleus when the beta-cateningene is mutated. This protein’s nuclear accumulation hasbeen shown in breast and abdominal fibromatosis(desmoid tumours), which helps distinguish it from otherspindle cell neoplasms that might develop there.