The expression of fibroblast growth factor receptor-3 in synovial osteochondromatosis of the temporomandibular joint.

Primary synovial osteochondromatosis (PSC) is a disease of unknown aetiology. It was reported recently that expression of fibroblast growth factor receptor-3 (FGFR-3) was observed specifically in PSC. We classified six cases of synovial osteochondromatosis (SC) of the temporomandibular joint (TMJ) into two types of SC, PSC (five cases) and secondary synovial osteochondromatosis (SSC) (one case), by means of clinical findings and haematoxylin and eosin stain. The five PSC cases were classified into three different phases according to Milgram's classification. Immunohistochemical staining of FGFR-3 was carried out for each SC case, along with specimens of internal derangement (ID) of the TMJ, and normal articular disc and synovial membrane. FGFR-3 was found in all three phases of PSC, but not in SSC, ID or normal TMJ. Moreover, in a comparison between cultured synovial cells of PSC (Phase III) and ID, reverse transcription-polymerase chain reaction revealed a stronger positive reaction in PSC. These results indicate that the synovial membrane in Phase III PSC can produce cartilage nodules, as in Phases I and II.