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Abstract

Fibrous dysplasia is a benign intraosseous lesion. It is not a neoplasm, but a developmental condition of the bone which appears similar to a tumor on radiological studies. Fibrous dysplasia is a sporadic condition caused by the inability to produce mature bone due to a genetic mutation in GNAS1; it can present in two clinical forms, monostotic or polyostotic. Fibrous dysplasia (FD) can be a component of McCune-Albright syndrome with both dermatological and endocrinological features. The femur, ribs and maxillofacial skeleton are the most common sites of involvement. Monostotic forms account for 80-85 % of the cases. It is caused by somatic activating mutations in the GNAS gene, which lead to constitutive activation of adenylyl cyclase and elevated levels of cyclic AMP. Herein, we report of six cases of fibrous dysplasia of the mandible and maxilla in our facility between November 2015 and October 2020 with mean age 44 years (range, 12-72 years). The maxilla was affected in the most cases (n=4), compared to mandible (n=2). The male to female ratio was 2:1. Some of the lesions showed ground-glass opacity on imaging. Microscopic examination of the biopsied specimens from each patient revealed fragments of relatively dense fibrous tissue containing irregularly shaped trabeculae of woven and lamellar bone. Some trabeculae were associated with newly forming, spontaneous bone derived from the surrounding fibrous tissue consistent with fibrous dysplasia. Each case demonstrated blending of fibrous and osseous tissue, with resultant secondary bony metaplasia, producing immature, haphazard, and weakly calcified woven bone. The clinical, radiographic, and the morphological appearance of FD exhibit a substantial overlap with other fibroosseous lesions, including malignant neoplasms, such as low grade osteosarcoma. FD involves the maxilla almost two times more often than the mandible. It frequently appears in the posterior region of the jaw bone and is usually unilateral. The importance of this study is to differentiate FD from other fibro-osseous lesions of the mandible and maxilla.

Biography

Dr. Daniela Proca is Professor of Clinical Pathology at Temple University, Philadelphia, Pennsylvania, USA and studies together with colleagues and residents bone and soft tissue lesions, particularly neoplasms.