Updated Australian guidelines on the management of melanomas recommend wider excision margins of 5-10mm for melanoma in situ.

The new advice, ratified by groups such as the Cancer Council, reflects recent studies showing higher recurrence rates for in situ melanomas excised with the 5mm margins recommended in previous 2008 melanoma guidelines.

The evidence-based recommendations, published in the MJA, state that excision margins for invasive melanomas remain unchanged.

However they note that a number of studies since 2008 have concluded that margins of at least 10mm are needed for in situ melanoma. In one of the larger studies, complete tumour clearance rates were 86% for 6mm margins and 99.4% for 12mm margins.

“The frequently recommended 5mm margin for melanoma in situ is inadequate,” the study authors concluded, recommending at least 9mm margins, similar to that recommended for early invasive melanomas.

The new guidelines therefore recommend that after initial excision biopsy, the radial excision margins, measured from the edge of the melanoma (or scar), should be 5-10mm, with the aim of achieving complete histological clearance.

Melanoma in situ of non-lentigo maligna type is likely to be completely excised with 5mm margins, whereas lentigo maligna may require wider excision.

The new guidelines also emphasise that minimum clearances from all margins should be assessed and stated on the pathology report.