The findings on the radiograph include:

• lesion is located at the distal femoral metaphysis, does not cross the physis, and extends in various directions

• destruction and loss of distinction between bone marrow and cortical bone

• wide transitional zone with indistinct borders

• aggressive periosteal reaction of sunburst type and Codman’s triangle

• invasion of adjacent soft tissue

• osteoid matrix

• no cortical expansion

MRI helps visualise the characteristics previously noted on the radiograph, showing tumour infiltration in the medullary canal and the metaphysis of the distal femur, not crossing the growth plate, with aggressive periosteal reaction (Codman's triangle), invasion, and formation of adjacent soft tissue mass, restricted diffusion, and strong contrast enhancement after injection.

Histopathology report (1):

• sample location: distal femur tumour

• staining method: Haematoxylin and Eosin

• macroscopic: specimen size 1.0 x 0.2 cm

• microscopic: tumour structure consists of bone fragments containing large, atypical nuclei with prominent nucleoli, along with haemorrhagic necrosis

• conclusion: high-grade osteosarcoma

Histopathology report (2) :

• sample location: soft tissue around distal femur tumour

• staining method: Haematoxylin and Eosin

• macroscopic: specimen core measuring 1.2 x 0.1 cm

• microscopic: fibrous tissue infiltrated by numerous large, atypical nuclei, with areas of osteoid formation

• conclusion: osteosarcoma with soft tissue invasion