LAUSR

Abstract Rationale: Giant synovial osteochondromatosis of the thigh is a highly unusual disease without standard diagnosis and curative managements so far. Our focus is to report a very rare case of giant synovial osteochondromatosis successfully operated by surgical treatment. The management of these unique cases has certain educational significance in clinical practice. Patient concerns: A 63-year-old previously healthy man presented to our institution with a 4-year history of continuous progressive hip pain and local numbness of right side in January 2018. One month ago, the patient felt that the above symptoms were aggravated, and the right hip and proximal thigh were significantly swollen. Diagnosis: Computed tomography and magnetic resonance imaging of the hip revealed the irregular mass in his right thigh. Post-operative pathology confirmed the diagnosis of synovial osteochondromatosis of the thigh. Interventions: Considering the large volume of the mass and possibility of malignancy, the patient underwent surgical exploration and complete tumor resection. Outcomes: The patient's neurological deficits and symptoms improved significantly after the surgery, and the postoperative period was uneventful at the 1-year follow-up visit. There were no complications associated with the operation during the follow-up period. Lessons: Taken together, the lesion's clinical features, imaging results, and pathological characteristics are unique. Synovial osteochondromatosis of the thigh, although rare, should be part of the differential diagnosis when the patient presents with local pain, numbness, swelling or other symptoms. We recommend surgical treatment for the occupying lesion when the tumor has caused symptoms or neurological deficits.