Fig. 3

Conventional AP, lateral radiographs and gross morphology of DF-LGCOS. a Conventional AP, lateral radiographs (top left and top middle) show an expansive osteolytic lesion in the diaphysis-metaphysis of the right distal femur with an ill-defined border and cortical destruction. Bone scintigraphy (top right) demonstrates increased uptake at the location of the lesion, but no suspicious uptake elsewhere. MRI with sagittal T1-weighted (bottom left) and fat-suppressed proton density-weighted (bottom middle) images, and axial T1-weighted and gadolinium-enhanced fat-suppressed T1-weighted images (bottom right) show the T1 hypointense, T2 hyperintense, and vividly enhancing lesion in the right distal femur as a large soft-tissue mass with cortical breakthrough and extra-osseous expansion. The combined imaging features are highly suggestive of an aggressive malignant lesion, with osteosarcoma, Ewing sarcoma, and chondrosarcoma being the main differential diagnostic considerations. b Gross specimen of DF-LGCOS, showing a white, fibrous tumor of the distal femur with cortical breakthrough and invasion of soft tissue. As such, the gross appearance of DF-LGCOS resembles DF