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BACKGROUND & OBJECTIVE: Synovial chondromatosis is a rare disease. It occurs as primary or secondary lesion with involvement of joint, tendon and bursa (extra articular) or combined. We present a case of subacromial chondromatosis with presentation of a large cystic lesion with rapid growth and containing numerous chondral particles.
CASE: The patient was a 16 year old boy admitted with a huge mass at right shoulder which was begun since 3 months. Sonography and CT scan showed a mass of 7 × 10 × 4 cm, which contained small particles. The patient was operated and a very large cystic mass with numerous rice bodies in it was removed. Pathologic examinations revealed primary synovial chondromatosis.
CONCLUSION: Synovial chondromatosis should be considered in differential diagnosis of cystic masses around the joints especially shoulder.