Background: Fibrous dysplasia of the rib is a common clinical entity, and usually identified incidentally with radiographic abnormality. However, they may undergo rapid enlargement which may be due to malignant degeneration.
Case Report: A 28-year-old woman was operated due to a growing and painful mass situated at the XI right rib. Once the diagnosis of fi brous dysplasia was established by incisional biopsy, the mass was resected totally. Histological examination was confirmed the previous diagnosis. She is well without any problems for 1 year after operation.
Conclusions: Though the possibility of malignant degeneration is low, complete resection will be more suitable instead of follow-up in such cases. Thus; symptomatic recovery will be provided, and there won’t be the risk of sarcomatous transformation.

Keywords: fibrous dysplasia, Monostotic, Ribs, Neoplasms, Thoracic Surgery