[Unusual clinical picture of a rotator cuff lesion].

A case of a 76 year-old male admitted to hospital because of a fast-growing tumour over his right shoulder is described. Malignity was initially suspected, but examination showed that the tumour was a cyst overlying, and arising from, the acromioclavicular joint. Furthermore we found a complete lesion of the rotator cuff. Acromioclavicular joint cysts are a known but unusual presentation of complete rotator cuff lesions, and their treatment includes anterior acromioplasty, acromioclavicular arthroplasty, and repair of the rotator cuff. Isolated surgical cystectomy is without purpose, as the cyst is bound to reappear. Surgical treatment is only indicated if there is severe pain, and/or unacceptable cosmetic problems.