Bone marrow edema as an independent imaging predictor of dedifferentiated chondrosarcoma

Dedifferentiated chondrosarcoma is the most aggressive subtype of chondrosarcoma; however, imaging features that independently distinguish it from other subtypes remain unclear. The purpose of this study was to identify independent imaging predictors of long bone dedifferentiated chondrosarcoma to signal for expedited biopsy and treatment.

This retrospective study incorporated consecutive patients undergoing resection at a tertiary center for primary intramedullary long bone chondrosarcoma between February 2001 and January 2024. Inclusion required preoperative MRI and postoperative pathological confirmation. Seven imaging features were analyzed. Multivariate regression investigated independent predictors of dedifferentiated versus non-dedifferentiated chondrosarcoma.

Sixty-seven patients were included. Of these, 23 (34%) patients presented with dedifferentiated chondrosarcoma, while 43 (64%) had conventional chondrosarcoma (21 grade 1, 18 grade 2, 4 grade 3) and one (1.5%) had grade 3 mesenchymal chondrosarcoma. On multivariate analysis, bone marrow edema was the only independent predictor of dedifferentiated status (p = 0.0091). This association persisted after controlling for age, sex, and tumor size (p = 0.0057). Bone marrow edema achieved a sensitivity and specificity of 87% and 68%, respectively, and the greatest area under the ROC curve among individual imaging features (AUC = 0.78, p = 0.0027), while the overall combined model achieved even greater discrimination (AUC = 0.87, p < 0.001).

Marrow edema was the only imaging feature that independently predicted dedifferentiated chondrosarcoma in multivariable analysis. Although incorporation of additional imaging findings provides the highest overall diagnostic accuracy, marrow edema alone demonstrates high sensitivity and is a readily identifiable marker that may prompt expedited biopsy when identified on routine preoperative MRI.