Clinicopathological Spectrum and Management of Aneurysmal Bone Cysts in Atypical Anatomical Location: A Comprehensive Review of Demographics, Presentation, Diagnosis, and Treatment Outcomes.

Introduction: Aneurysmal bone cysts (ABCs) are benign but locally aggressive osteolytic lesions characterized by blood-filled cystic spaces separated by fibrous septa containing osteoclast-like giant cells and reactive bone. Although commonly affecting the metaphysis of long bones in children and adolescents, ABCs may occur in atypical anatomical locations, creating diagnostic and therapeutic challenges. The aim of this study was to review the demographic characteristics, clinical presentation, radiological and histopathological features, diagnostic challenges, and current management strategies of atypically presenting ABCs. Materials and Methods: A narrative review was performed using articles published in the Journal of Orthopaedic Case Reports from 2011 to 2026. Forty-two records were initially identified (41 case reports and 1 case series); 15 were excluded after initial screening, and 10 additional reports were excluded at full-text assessment because they described conventional metaphyseal ABCs, leaving 17 reports (16 case reports and 1 case series) for the atypical-location review. Because this was a narrative review restricted to a single journal, no pooled effect estimates or formal comparative treatment conclusions were attempted. Results: ABCs predominantly occur during the first two decades of life and commonly involve the distal femur, proximal tibia, proximal humerus, and spine. Pain and swelling are the most frequent presenting symptoms. Radiographs typically demonstrate expansile osteolytic lesions with a multiloculated appearance, while magnetic resonance imaging frequently reveals fluid-fluid levels. Histologically, lesions consist of blood-filled spaces, fibroblastic septa, osteoclast-like giant cells, and reactive woven bone. Management options include curettage with bone grafting, sclerotherapy, en bloc resection, and reconstruction depending on lesion location and aggressiveness. Recurrence rates vary between 10% and 30%, with lower recurrence following complete excision. Conclusion: ABCs exhibit a wide clinicopathological spectrum. In atypical anatomical locations, diagnosis requires careful clinicoradiological correlation and histopathological confirmation. Management should be individualized according to lesion biology, anatomical constraints, skeletal maturity, and functional requirements; however, treatment effectiveness and recurrence rates cannot be established reliably from the predominantly case-report-based evidence reviewed here.