Patients with increased numbers of moles on their limbs are at an increased risk of developing melanoma.
Melanoma cases annually continue to rise with nearly 16 000 cases a year, that’s about 44 new cases a day in the UK (1). Podiatrists are well placed to keep a check on pigmented lesions arising on the feet and legs. When considering a patient’s risk for melanoma, its important to remind ourselves of the main risk factors for melanoma (2-6):
1. Fair skin type – often accompanied by blue or green eye colour and fair hair. 2. A history of intermittent and excessive UV exposure and sunburn. 3. A family history of melanoma. 4. A high number of benign naevi (moles).
The latter factor is an interesting one. Studies have shown how people with higher body mole counts are at an increased risk of melanoma. Moles develop usually as a result of sun exposure in childhood but there are also genetic factors involved in the numbers of naevi a person may have. Of course, moles themselves are not melanoma. Around 30% of melanoma are thought to develop from pre-existing naevi – the majority (around 70%) arise “de novo”.
Counting all of ones naevi can be a difficult task and in a clinical setting for a podiatrist completely impractical but in assessing mole counts a recent paper, Wei et al., (7) in the Journal of the American Academy of Dermatology, demonstrated that an fair estimation can be made just by looking at the limbs. Using data sets from a number of surveys where participants were asked to count their moles on their legs and categorise them into groups: 1-2, 3-5, 6-9, 10-14, 15-20, or >21. Analysis of the data showed the greater the number of moles on the limbs, the greater the risk. In the combined analysis, individuals with 6 to 14 nevi or > 15 nevi on the extremity had an increased risk of 2.76 and 2.79 respectively of developing melanoma.
Sun protection advice for our patients is always good but recognising those at an increased risk can be helpful to identify those at a higher risk to promote good skin care and screening.
References
1. Cancer Research UK. Melanoma Cancer Statistics 2018 [cited 2018 1st October ]. Available from: https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/melanoma-skin-cancer#heading-Zero. 2. MacKie RM, Hauschild A, Eggermont AM. Epidemiology of invasive cutaneous melanoma. Ann Oncol. 2009;20 Suppl 6:vi1-7. 3. MacKie RM. Incidence, risk factors and prevention of melanoma. Eur J Cancer. 1998;34(Supplement 3):3-6. 4. Gandini S, Sera F, Cattaruzza MS, Pasquini P, Zanetti R, Masini C, et al. Meta-analysis of risk factors for cutaneous melanoma: III. Family history, actinic damage and phenotypic factors. Eur J Cancer. 2005;41(14):2040-59. 5. Gandini S, Sera F, Cattaruzza MS, Pasquini P, Picconi O, Boyle P, et al. Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer. 2005;41(1):45-60. 6. Gandini S, Sera F, Cattaruzza MS, Pasquini P, Abeni D, Boyle P, et al. Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi. Eur J Cancer. 2005;41(1):28-44. 7. Wei EX, Li X, Nan H. Extremity nevus count is an independent risk factor for basal cell carcinoma and melanoma, but not squamous cell carcinoma. J Am Acad Dermatol. 2019;80(4):970-8.