Chondroblastoma containing aneurysmal bone cyst (ABC)-like changes in a 13-year-old boy. A sagittal fat-suppressed T2-weighted magnetic resonance image of the knee shows a well-defined, lobulated lesion involving the posterior aspect of the proximal tibial epiphysis (arrows) corresponding to the chondroblastoma. The lesion is cystic and multiseptated containing a fluid-fluid level (arrowhead). Note the extensive, surrounding bone marrow and soft-tissue edema (asterisks) characteristic of chondroblastomas. After resection, the diagnosis of chondroblastoma with ABC-like changes was confirmed