Figure 1. (A) Anteroposterior and lateral radiographic images from the previous hospital. The left femur showed extensive erosion of the medial cortical bone. (B) CT scans in the coronal and sagittal planes. The medial cortical bone of the femur showed segmental erosion extending approximately 15 cm, with localized thinning of the cortical bone. (C) Representative MRI images, from left to right: T1-weighted, T2-weighted, and STIR sequences. The left femur had a large lesion centered on the medial cortex, with a low-to-isointense signal on the T1-weighted image, high signal intensity on the T2-weighted image, and high signal intensity on the STIR image. (D) PET-CT images of the transverse section combined with a CT image of the coronal plane. PET-CT images of the transverse section at each location are shown. Hypermetabolic activity is observed in both the medial cortex and intramedullary cavity, with the cortical pseudocavity showing higher metabolic activity than the intramedullary cavity. CT – computed tomography; MRI – magnetic resonance imaging; STIR – short tau inversion recovery; PET – positron emission tomography.