Fibrous dysplasia: clinical and pathologic characteristics, surgical approaches, and outcomes in a large Italian cohort.

Fibrous dysplasia (FD) is a rare benign bone disease caused by postzygotic activating mutations in the GNAS gene, leading to replacement of normal bone with fibrous tissue. It may be monostotic or polyostotic, often asymptomatic but sometimes associated with pain, deformity, or fractures. Management is mainly surgical in symptomatic or complicated cases. This retrospective study analyzes a large FD cohort to identify determinants of treatment and outcomes, with a focus on pain and its evolution. The primary aim was to assess factors influencing surgical indication, while the secondary aim was to evaluate predictors of outcome in surgically treated patients, particularly symptom persistence at follow-up. A total of 227 patients were included. Mean age at diagnosis was 35.5 years (range 2-86 years); 79.3% had monostotic and 20.7% polyostotic FD. Pain was the most common presentation (62.6% at diagnosis; 78.4% during disease course), followed by incidental findings (21.6%), fractures (11.5%), and mass (4.4%). Surgery was performed in 51.6% of patients (127 lesions). Surgical patients were younger and had larger lesions and higher Mirels' scores (all p < 0.001), although Mirels' score showed only moderate predictive accuracy for surgery (area under the curve (AUC) 0.71). At a mean follow-up of 4.5 years, persistent pain was present in 24.1% of patients, with no significant difference between surgical and nonsurgical groups. Surgery was not an independent predictor of pain resolution in multivariable analysis. Postoperative complications occurred in 17.3% of procedures, with 7.1% requiring multiple revisions; rates were higher in polyostotic disease (21.3% versus 6.7%, p = 0.004). Our findings suggest that pain alone should not be used as an indication for surgery in FD, as it was not a reliable predictor of outcome in our study. Surgical decisions for pain relief should therefore be made with caution, and patients should be informed about the risk of persistent symptoms. Conservative, multidisciplinary management-including bisphosphonates, monoclonal antibodies, and psychological support-should be considered first-line, as it may improve symptoms and quality of life.