Lifetime risk of mole transforming to melanoma is very low

Question What is the risk that any given mole will become a melanoma?

Synopsis This is an interesting question, and may be helpful as we talk to our patients about moles and melanoma. The authors performed a decision analysis by taking data from a variety of sources, including surveys of the number per adult of melanocytic naevi at least 2-3 mm in diameter and a community based pathology database of skin biopsies. They created a theoretical model to determine the transformation rate, and they stratified their findings by age. The risk that any single mole on a 30 year old will become a melanoma by age 80 was 38/100 000 in men and 11/100 000 in women. The lifetime risk of transformation to melanoma gradually increases in men from 31.6/100 000 in 20 year olds to 50.1/100 000 in 50 year olds (that is, from 1 in 3000 to 1 in 2000).

Bottom line Using a theoretical model and existing sources of data, the authors estimate that the lifetime risk that a mole will become a melanoma in a 50 year old man is 1 in 2000 and in a 50 year old woman is 1 in 9000. These findings call into question the cost effectiveness of surveillance programmes and frequent excisions, especially for young patients or patients at low risk.

Level of evidence 2c (see www.infopoems.com/resources/levels.html); “outcomes” research