Pigmented villonodular synovitis of the shoulder: review and case report.

Pigmented villonodular synovitis (PVNS) as reviewed in detail elsewhere most frequently involves the knee and finger synovial structures; shoulder involvement is rare: A search through the English literature yielded 18 publications describing 25 cases of PVNS affecting the shoulder joint. Analyzing these reports we found the clinical and radiological findings generally to be nonspecific, often mimicking a malignancy, as in the case presented here of a 16-year-old boy with painful swelling in the area of the left proximal humerus. Magnetic resonance imaging showed a suspected malignant soft tissue mass involving the shoulder capsule and measuring 7.5 x 6 x 4 cm. Preoperatively the patient could recall no trauma; however, postoperatively he did report a distortion trauma of the affected shoulder following a bicycle accident. Intraoperatively, two tumors were found infiltrating the axillary vessels and nerve and tendon structures originating in the capsule of the shoulder joint. Rapid sections of the tissue revealed no signs of malignancy; further pathohistological examination revealed localized PVNS. Preoperatively, the shoulder joint was not suspected as the primary site of origin of the tumor because the patient had no complaints or functional deficits of the shoulder. The clinical presentation of such a PVNS lesion over the proximal humerus is unusual and to date has only twice been described in the literature.