≥5 cm Tumor with Cortical Breach Predicts Recurrence and Distinguishes ACT from Enchondroma in Long Bones

Purpose: This study aimed to validate potential clinical and radiological features for distinguishing enchondromas from atypical cartilaginous tumours (ACT) and to analyse the association between maximum tumour diameter and local recurrence of enchondromas. It is important to note that this research serves as a validation cohort rather than proposing a new diagnostic framework. Materials and Methods: This retrospective study reviewed the clinical data of 50 patients pathologically diagnosed with enchondroma or ACT and treated in our center between 1 January 2015 and 1 June 2024. Imaging characteristics, recurrence outcomes and other variables were compared among patients, and chi-square tests were used to assess the influence of maximum tumour diameter and other relevant factors on the recurrence rate. This study has been approved by the ethics committee of our institution. Results: Patients with a maximum tumor diameter ≥ 5 cm exhibited a higher recurrence risk (recurrence 8 % vs. non-recurrence 0 %, P = 0.01, P < 0.05). This difference is statistically significant and may aid in distinguishing enchondroma from ACT. Moreover, all recurrent cases exhibited cortical bone destruction, which further validates the importance of this imaging feature as a key differentiating point. The primary treatment consisted of curettage combined with bone grafting, yielding an overall favorable prognosis. Discussion: A maximum tumor diameter of ≥5 cm and cortical bone destruction can be considered important predictive factors for local recurrence, and they may also assist in differentiating between atypical cartilaginous tumors (ACTs) and enchondromas. Based on our findings, we are more inclined to consider lesions ≥5 cm as ACTs, particularly when accompanied by cortical destruction, as these features suggest a more aggressive biological behavior. Therefore, we recommend performing extended curettage combined with intraoperative electrocautery or other effective local adjuvant techniques in such cases to achieve adequate tumor control and reduce the risk of recurrence.