Monostotic craniofacial fibrous dysplasia: report of two cases with interesting histology.

Fibrous dysplasia (FD) is a relatively rare osseous disease of unknown etiology, wherein the normal bone is replaced by collagen-rich tissue, comprising of fibroblasts and variably abundant immature woven bone. Clinically, it may involve a single bone or multiple bones. It commonly arises in the jaw bone, skull, rib, and proximal femur. Those arising in the skull and the jaw are together termed "craniofacial fibrous dysplasia." The differential diagnosis at this location includes meningioma and metastatic carcinoma. In this report, we highlight two diagnostically challenging cases presenting with orbital swelling and headache as the main complaints. Our first case was misinterpreted as meningioma on intraoperative squash smear, and paraffin sections revealed characteristic features of FD. The second case highlights the morphological feature of non-specific cystic degeneration occurring in FD. Radiographs in such cases show cystic swelling, which is indicative of a secondary aneurysmal bone cyst.