Histopathology and molecular hallmarks of Case #2: The tumour showed heterogeneous morphology. Most cells were spindle-shaped but giant cells with segmented nuclei were also present. Focally, transitions into higher differentiated lipomatous tissue were noticed (A). Other areas were of osteoblastic/osteosarcomatous (B) and fibrosarcomatous appearance (C). Fluorescence in situ hybridisation of the MDM2 gene revealed highly amplified clusters in the lipomatous (D, left), fibrosarcomatous and the osteosarcomatous regions (D, right).