Recognition and Recurrence of Aneurysmal Bone Cyst Secondary to Giant Cell Tumor: A Case Series and Review Of The Literature.

Background: Aneurysmal bone cysts (ABCs) are rare, benign bone lesions with distinct genetic and pathological characteristics. Secondary ABCs arising from giant cell tumors (GCTs) are associated with higher recurrence rates compared to primary ABCs. This study aimed to evaluate recurrence rates and risk factors for primary ABCs, secondary ABCs in GCT, and GCTs, with a focus on radiologic and clinical predictors. Methods: This retrospective cohort study analyzed 44 patients with histologically confirmed primary ABC (n=24), secondary ABC in GCT (n=8), or GCT (n=12), treated surgically with adjuvants between 2010 and 2020. Tumors were staged using the Enneking/MSTS system, and recurrence rates were assessed using Kaplan-Meier survival analyses and Chi-square tests. The mean follow-up period was 49.4 months. Results: The overall recurrence rate was 11%, with a 5-year recurrence-free survival rate of 89%. Recurrence-free survival was 92% for primary ABCs, 92% for GCTs, and 75% for secondary ABCs. Significant risk factors included soft tissue extension in primary ABCs (p = 0.037) and mixed radiologic appearance in GCTs (p = 0.033). Secondary ABCs were more common in patients over 20 years and often presented with multiloculated cystic areas. Conclusion: Recurrence rates are similar among primary ABCs, secondary ABCs, and GCTs. However, secondary ABCs exhibit recurrence behaviors closer to GCTs, particularly in patients with advanced age and complex radiological features. These findings highlight the importance of meticulous tumor resection and the careful use of adjuvants to reduce the risk of recurrence.