Journey and Roadblocks in the Management of Aneurysmal Bone Cysts in Patients with Unusual Presentations.

Introduction: To describe the clinical, radiological, and histopathological spectrum of aneurysmal bone cysts (ABC) with unusual presentations and to highlight diagnostic pitfalls and management challenges in these patients. Materials and Methods: This ambispective study included 20 cases with ABC or ABC-mimicking lesions treated between March 2022 and November 2024 at a tertiary care hospital. Patients were eligible if they had at least one atypical feature. These included uncommon age, rare anatomical location, atypical radiological appearance suggesting alternative diagnoses (including sarcoma), or an inconclusive biopsy report. All patients underwent standardized clinical, radiological, and histopathological evaluations. Selective use of core/open biopsies and intraoperative frozen sections was included. Management was tailored to site- and lesion-specific factors. Results: Of 20 cases, 11 were males, and 9 were females, with a mean age of 20.3 years (range 5-45 years); most patients were younger than 10 years or older than 30 years, which is outside the usual second-decade peak for ABC. Lesions affected multiple rare sites, including the shaft of the ulna, glenoid, acetabulum, talus, calcaneum, metatarsal, clavicle, wing of the sphenoid, rib, and neck of the femur. Radiological imaging suggested ABC in 13 patients, but alternative diagnoses such as sarcoma, giant cell tumor, fibrous dysplasia, and Brown's tumor were reported in the remainder, and the final histopathology confirmed a range of entities, including primary and solid variant ABC, simple bone cyst, chondroblastoma, fibrous dysplasia, and osteoclast-rich lesion secondary to Vitamin D deficiency. Most patients were treated with intralesional polidocanol injection and extended curettage with allogenic bone graft, whereas a few underwent wide resection or adjuvant denosumab; over a mean follow-up of 15 months, one patient developed recurrence after curettage, and one presented with a pathological fracture. Conclusion: ABC with unusual age, location, or non-typical imaging and biopsy findings can closely mimic more aggressive pathologies and complicate decision-making. Systematic metabolic evaluation, careful correlation of radiology with core or open biopsy and intraoperative frozen section, and tailoring of treatment to site, size, and confirmed pathology can improve diagnostic accuracy and optimize outcomes in such challenging cases.