Fibrous dysplasia protuberans refers to a benign fibro-osseous exophytic mass originating in the intra-medullary cavity of an adjacent bone. A case of fibrous dysplasia protuberans is hereby presented, manifesting as an exudative pleural effusion in a 49 years old male with history of McCune-Albright syndrome. This case represents the first reported case of fibrous dysplasia protuberans in a patient with McCune-Albright syndrome. Without a high index of suspicion, detailed radiographic imaging and meticulous histological examination, this benign bony excrescence is likely to be misdiagnosed, especially in a patient with no previous history of fibrous dysplasia.