Step 4: Imaging

Objective :

An MRI is the best investigation for a rapidly growing deep soft tissue tumour

Tip 1

The tumour is very heterogenous and contains a lot of fluid.

Tip 2

You can see the tumour pressed up against the sciatic nerve, which here is just splitting into its two terminal branches.

Tip 3

The tumour does not involve the major blood vessels.


What is the most likely diagnosis?

Soft Tissue Sarcoma

Tip 6

This story and imaging are very suspicious for a soft tissue sarcoma. It may be a malignant peripheral nerve sheath tumour arising from the sciatic nerve.



Tip 7

This is very unlikely in the absence of trauma, anticoagulants or a bleeding disorder.



Tip 8

Sometimes lipomas can be large and deep, but an MRI scan would show a lesion that looked the same signal as fat. MRI is the best modality for distinguishing a large lipoma from a sarcoma.

More Info Next Step

It can be difficult to know which imaging to arrange for. An ultrasound scan is cheap and more accessible, but is unreliable in distinguishing between malignant and non-malignant masses. In the clinical situation of a rapidly growing deep mass an urgent MRI is warranted.