Aneurysmal bone cyst of the pelvis: systematic literature review

Aneurysmal bone cysts (ABCs) are rare benign, vascular, and osteolytic bone lesions. Pelvic ABCs account for 8-12% of these tumors and no clear guidelines for their treatment are available. To the best of our knowledge, this is the first systematic literature review regarding pelvic ABCs. Our objective was to identify treatment modalities and assess bone healing, measured as the degree of radiological ossification. Searches were conducted in PubMed, Cochrane Library, and Web of Science. Based on the scarcity of reports, inclusion criteria were kept broad and included primary or recurrent pelvic ABCs, with a minimum followup of 1 year and available information on radiological ossification. Data were extracted at the individual patient level and grouped according to treatment modality. Forty-nine studies reporting on 194 patients were included from the study. The level of evidence was low (29 case reports and 20 retrospective case series), and the reporting of outcomes was inconsistent. Five major treatment groups were identified and divided into 11 subgroups. The largest subgroup was curettage (23%), followed by selective arterial embolization (20%). Most ABCs were located in the ilium. Variations in mean tumor size (4.5-22.2 cm) and degree of ossification (60-100%) depended on the treatment modality. Overall, in 77% of the cases, the cyst ossified completely. Recurrence was reported in 22 patients (11%) and two patients (1%) died during the course of the treatment. This systematic review provides the first comprehensive overview of pelvic ABC treatment modalities and their radiological and clinical outcomes. Neoadjuvant scleroembolic treatments appear to be used most in recent years, but further comparative studies and better quality of reporting are needed to determine their effectiveness.