56/ F Shoulder Mass

. Rt. Shoulder mass for 1year, pain for 7 months
. Needle Biopsy
Low cellularity, Mild atypism, No necrosis
Mitosis : 5 in needle biopsy
Bx Dx : Spindle cell malignancy

• Dx : Fibromatosis
• Fibromatosis: Pleomorphism and necrosis are absent but mitotic activity up to about 5 per 10 hpf can sometimes be found.
• Beta-catenin staining in nuclei is helpful.