ORIGINAL ARTICLE Aneurysmal bone cyst of the clavicle: a series of 13 cases Courtney L. Kaiser, BA, Caleb M. Yeung, MD, Kevin A. Raskin, MD, Santiago A. Lozano-Calderon, MD, PhD* Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Massachusetts General Hospital—Harvard Medical School, Boston, MA, USA Background: Aneurysmal bone cyst (ABC) is a benign but locally aggressive bone tumor occurring most commonly in the first 2 decades of life. The clavicle is a rare location for tumors, and ABCs of the clav- icle have been sparsely described in the literature. We present the largest known series of ABCs of the clavicle to describe this rare condition. Methods: Patients were identified retrospectively from an orthopedic oncology database to obtain demo- graphic, diagnostic, and treatment information. A literature search was performed to identify all English language reports of ABC of the clavicle. Results: We identified 13 patients with ABC of the clavicle, 77% of which were in the acromial end. Most patients (77%) presented with pain or swelling or both. The initial treatment in 11 patients was by curettage, with or without allograft bone packing, and 1 underwent resection/reconstruction of the lateral clavicle. Seven patients (58%) had 1 or more recurrences at an average of 6 months, for which 2 were treated with partial resection of the clavicle. Conclusions: ABC of the clavicle is a rare condition that we found to occur most frequently in the ac- romial end of the bone. Most patients were initially treated with curettage and showed a higher rate of recurrence than in other locations. The unique anatomy of the clavicle makes resection a feasible and very functional option, especially if the coracoclavicular ligaments can be preserved. However, the potential resulting deformity may cause patients to opt for a less aggressive and, consequently, less effective treat- ment method. Level of evidence: Level IV; Case Series; Treatment Study © 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Aneurysmal bone cyst; clavicle; benign tumor; shoulder; orthopedic oncology; recurrence Aneurysmal bone cyst (ABC) is a benign, locally aggres- sive bone tumor that is most commonly seen in the skeletally immature, with 80% occurring in patients aged younger than 20 years. The literature reports either no or a slight female predilection. 2-4,6,18,19 ABCs account for 1% to 3% of all benign osseous tumors and are most frequently seen in the long tubular bones, vertebrae, pelvis, and scapula. 4,6,19 The Massachusetts General Hospital Institutional Review Board approved this study (IRB Protocol#: 2013P002662/MGH). *Reprint requests: Santiago A. Lozano-Calderon, MD, PhD, Musculoskeletal Oncology Service, Massachusetts General Hospital—Harvard Medical School, 55 Fruit St., Boston, MA 02114, USA. E-mail address: slozanocalderon@mgh.harvard.edu (S.A. Lozano- Calderon). www.elsevier.com/locate/ymse ARTICLE IN PRESS 1058-2746/$ - see front matter © 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. https://doi.org/10.1016/j.jse.2018.06.036 J Shoulder Elbow Surg (2018) ■■, ■■–■■