Subacromial Impingement Syndrome Caused by a Voluminous Subdeltoid Lipoma

Subacromial impingement syndrome is a clinical diagnosis encompassing a spectrum of possible etiologies, including subacromial bursitis, rotator cuff tendinopathy, and partial- to full-thickness rotator cuff tears. This report presents an unusual case of subdeltoid lipoma causing extrinsic compression and subacromial impingement syndrome. The patient, a 60-year-old man, presented to our institution with a few years' history of nontraumatic, posteriorly localized throbbing pain in his right shoulder. Despite a well-followed 6-months physiotherapy program, the patient was still suffering from his right shoulder. The MRI scan revealed a well-circumscribed 6？cm × 2？cm × 5？cm homogenous lesion compatible with a subdeltoid intermuscular lipoma. The mass was excised en bloc, and subsequent histopathologic examination confirmed a benign lipoma. At 6-months follow-up, the patient was asymptomatic with a complete return to his activities. Based on this case and a review of the literature, a subacromial lipoma has to be included in the differential diagnosis of a subacromial impingement syndrome refractory to nonoperative treatment. Complementary imaging modalities are required only after a failed conservative management to assess the exact etiology and successfully direct the surgical treatment. 1. Introduction Subacromial impingement syndrome is a clinical diagnosis encompassing a spectrum of possible etiologies, including subacromial bursitis, rotator cuff tendinopathy, and partial- to full-thickness rotator cuff tears [1]. Despite some controversy regarding the significance of this entity [2], most authors recognize that subacromial impingement syndrome results from either intrinsic tendon degeneration or extrinsic compression, which can be primary or secondary. Primary structures responsible for extrinsic compression include the anterior acromion, coracoacromial ligament, and acromioclavicular joint. Secondary causes of impingement are multiple and can include tuberosity fracture nonunion or malunion, a mobile os acromiale, calcific tendinitis, instability, or iatrogenic factors [1]. This report presents an unusual case of subdeltoid lipoma causing secondary extrinsic compression and subacromial impingement syndrome. 2. Case Report A 60-year-old man (a maintenance employee) presented to our institution with a few years’ history of nontraumatic, posteriorly localized throbbing pain in his right shoulder. He also reported a traction injury to the same shoulder a few months ago while he was pulling on a cord trying to start a lawn mower. Since this episode, he