The patient went on to have surgery.

Histology

MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of moderately hypercellular tissue. These contain haphazardly arranged and irregularly shaped trabeculae of woven bone, some with incomplete osteoblastic rimming. Spaces between trabeculae are filled with a loose fascicular and storiform arrangement of spindle cells. These have uniform nuclear features. No mitotic figures or areas of necrosis are seen. Immunohistochemistry shows weak positive staining for smooth muscle actin (SMA) in the spindle cells. No staining for epithelial membrane antigen (EMA) or progesterone receptor (PgR) is seen. The features are of fibrous dysplasia. No evidence of malignancy is seen.

FINAL DIAGNOSIS: fibrous dysplasia.