Orthopaedic oncology Generic structured oral examination question 2: Margins

EXAMINER: What do you understand by a marginal margin?

CANDIDATE: A marginal margin, as described by Enneking, is when the resection line passes through the reactive zone of the tumour being excised.¹

EXAMINER: Explain to me what you mean by the reactive zone.

CANDIDATE: Tumours grow in a centifugal fashion and this leads to compression and subsequent atrophy of the surrounding tissue forming a pseudocapsule. Outside the pseudocapsule is an area of oedema where inflammatory cells and micronodules of tumour are present. This is the reactive zone. Hence, if a resection line passes through this reactive zone, as in a marginal margin, then micronodules of tumour are likely to be left behind, increasing the risk of a local recurrence.

EXAMINER: So what other margins did Enneking describe and what do you understand by them?

CANDIDATE: Enneking described three other possible margins. He described intra-lesional margins, where the resection line passes through the tumour leaving macroscopic deposits of tumour in the surgical wound. He described wide margins, where the resection line passes outside the reactive zone and the tumour is excised with a surrounding cuff of normal tissue. In wide margins it is still possible that tumour will remain in the form of skip lesions. Finally, he described the radical margin, where the entire compartment in which the tumour resides is excised en bloc, in theory removing the entire tumour.

1. Enneking WF, Spanier SS, Malawer MM. The effect of the anatomic setting on the results of surgical procedures for soft parts sarcoma of the thigh. Cancer 1981;47 (5):1005–1022