Lipoma Arborescens of the Subdeltoid Bursa Associated With Rotator Cuff Tear: A Case Report

Lipoma arborescens is a rare synovial lesion characterized by villous proliferation of the synovial membrane and replacement of subsynovial tissue with mature fat cells. The knee joint is the most frequently affected site, particularly in the suprapatellar pouch. However, there have been few reports regarding shoulder involvement, including the glenohumeral joint and subacromial subdeltoid bursa, associated with rotator cuff tear. This article reviews the case of a 67-year-old man who presented with lipoma arborescens of the left shoulder, associated with a rotator cuff tear. Sonography revealed a fluid collection with thickening of the synovial membrane with hyperechoic villous proliferation, located in the subdeltoid bursa. An arthroscopic synovectomy and rotator cuff repair were performed. Arthroscopic findings included yellow frond-like synovial proliferation of the synovium. Postoperatively, the patient was asymptomatic, and the lesion did not recur. Although magnetic resonance imaging is the first-line imaging modality for diagnosis of this lesion, sonography may be used initially for evaluation of chronic joint swelling. In addition, it can be useful for detection of recurrence after synovectomy. This case illustrates the typical sonographic features of lipoma arborescens.