Giant cell tumor of distal femur. A, Radiograph shows lytic lesion in the distal femoral metaphysis and epiphysis. B, T1-weighted coronal image confirms a well-demarcated intermediate-signal lesion replacing the normal hyperintense fatty marrow of the distal femur. C, Fat-suppressed proton density-weighted coronal image shows heterogeneous hyperintense tumor in a similar distribution. There is subtle cortical destruction of the lateral metaphyseal cortex (arrow).