Orthopaedic oncology Structured oral examination question 9: Lipoma
EXAMINER: This is an MRI of a patient who has presented with a painless mass on the lateral aspect of his right elbow. To orientate you the round structure (labelled A) is the radial head. Tell me about the lesion adjacent to it, which is labelled B. (Figure 7.9.)
CANDIDATE: There is an intramuscular mass in the extensor compartment adjacent, and lateral, to the radial head. The mass itself appears bland and is of the same intensity as the subcutaneous fat, suggesting a diagnosis of an intramuscular lipoma.
Figure 7.9 Lipoma.
EXAMINER: What is a lipoma?
CANDIDATE: A lipoma is a benign tumour of mature adipocytes, identical to the surrounding adipose tissue, and showing little variation of cell size or shape.
EXAMINER: And how would you treat this lesion?
CANDIDATE: I would want to start by taking a history and examination, in particular looking for any abnormal features like pain or distal neural compromise, which might suggest a more aggressive lesion than a simple lipoma, and alter my management. Also, this is only a single image of the lesion and I would want to see the rest of the scan and discuss it with the sarcoma MDT. Bland, innocent-looking lesions are usually treated with excision biopsy with a marginal margin. If there is any doubt then a biopsy should be taken prior to excision. Histology of lesions below the fascia, like this one, often come back labelled as
atypical lipomas by the histologist, despite very bland appearance on MRI.
EXAMINER: What do you mean by an atypical lipoma?
CANDIDATE: The term is quite controversial and the literature often refers to them as lipoma-like liposarcomas. In essence, an atypical lipoma is a lipoma with some slightly atypical features but no evidence of malignancy. The histology of such lesions shows variation of adipocyte size, in contrast to the bland adipocytes of a simple lipoma, and nuclear atypia, as well as the presence of lipoblasts. These lesions are benign and management is still with marginal excision but they do have a low rate of local recurrence.1
1. Beckingsale TB, Gerrand CH. The management of soft-tissue sarcomas. Orthopaed Trauma 2009; 23(4):240–247
