What sequence is best for assessing bone marrow involvement?
When marrow is fatty (as in this case) T1 non-fat sequences are easiest to interpret.
What should you always do before biopsying a likely sarcoma? (other than the usual consent, coagulation etc...)
It is essential to discuss the case with the surgeon / unit who will be resecting the tumour as the biopsy track also needs to be excised. A poorly planned biopsy can ruin the ability to perform limb sparing surgery or make reconstruction difficult.
MRI of the thigh confirms the presence of a large heterogeneous mass extending into all compartments. It enhances brightly but irregularly with areas of presumed necrosis. Erosion of the femur is also shown without however evidence of extension into the bone marrow on axial images. There is extensive oedema extending proximal and distal to the mass.