Changing moles - red flag symptoms

An overview of red flag symptoms to consider when assessing changing moles, including signs that may indicate suspected melanoma.

Malignant melanoma
Malignant melanoma

Red flag symptoms

  • Appearance of a new changing mole
  • Changes in size of an existing mole, especially irregular changes in the lesion borders
  • Changes in colour, especially irregular pigment, including development of lighter areas (regression)
  • Changes in moles larger than the end of a pencil (6mm)
  • Moles that bleed spontaneously and have no history of trauma
  • A mole that looks different from all of the other moles around it

Malignant melanoma is a form of skin cancer with 14,509 new cases diagnosed in the UK in 2013.1 It is more common in younger people and is currently the most common form of cancer among the 15-34 years age group. In the UK, malignant melanoma incidence rates have increased 360% since the 1970s.

Early referral, diagnosis and treatment are essential in reducing death rates, which currently account for 1% of all cancer deaths per year. In 2014, there were 2,459 deaths from malignant melanoma in the UK,1 1,431 males and 1,028 females.

Possible causes of changing pigmented lesions

  • Benign naevi
  • Dysplastic naevi
  • Seborrhoeic keratoses and warts
  • Malignant melanomas
  • Haemangiomas
  • Lentigo maligna
  • Pigmented basal cell carcinomas


Patients with skin types 1 and 2 are at higher risk of developing malignant melanoma than those with darker skin types.

Sun exposure is the key factor, especially sun exposure in childhood resulting in sunburn.

Men are at higher risk of developing malignant melanoma on their back, while for women the risk is greater on their legs, because these areas are more commonly exposed to sunlight. The increase in use of sunbeds and foreign travel has also contributed to increased UV exposure.

A family history is significant; 8% of patients with a newly diagnosed malignant melanoma will have a first-degree relative with the condition and 1-2%, a more distant relative.2

Malignant melanoma is more common in people who have large numbers of naevi and serial photography can be useful to monitor changes and the development of new naevi in such patients.

The ABCDE (Asymmetry, Border, Colour, Diameter, Evolving) rule can be helpful in the assessment of pigmented lesions.

Questions to ask

When a patient presents with concern about a mole, ask them the following questions:

  • How long has it been present?
  • Has there been any recent change, particularly the border, size and pigment? This should include lightening areas of pigment, which may represent regression, seen in malignant melanoma, as well as new darker areas. Even changes in pigment are less important than variations.
  • Has the mole suddenly started to bleed, with no history of trauma?
  • Ask about their skin type and history of sun exposure, including childhood experiences of the sun.
  • Ask where they have lived. People who live nearer the equator are at increased risk.
  • Ask if they spend a lot of time working outdoors, or have hobbies such as golf or gardening.
  • Do they use sunbeds? Sunbed use continues to be popular among younger patients, especially those who have a sunbed at home.


When checking patients' moles, always check the whole body, with special attention to the back in men and the legs in women.

Remember that the patient may not have noticed a mole in areas that are not readily visible, although it is not uncommon for patients to report the concerns of partners and relatives who have noticed suspicious moles.

The ugly duckling sign can be helpful, where a mole that looks significantly different from any others should be examined more carefully. This is especially useful in patients who have lots of abnormal-looking moles, which are unlikely to all be malignant melanoma.


Dermoscopy can be helpful in checking pigmented lesions. Benign seborrhoeic keratoses can look very dark and sinister, but have a characteristic appearance under the dermatoscope.

A little training in using a dermatoscope can be especially beneficial in diagnosing keratoses and vascular lesions, which may reduce unnecessary anxiety and referrals for patients.

It is not recommended to biopsy pigmented lesions because malignant change may not be visible throughout a lesion. If a pigmented lesion is suspicious, the whole pigmented area should be excised and examined.

The exception to this is large pigmented areas in the elderly, which may represent lentigo maligna, where a wide excision may involve extensive and disfiguring surgery.

When to refer

Any moles thought to be malignant melanoma should be referred under the two-week wait referral scheme.

This should include any new abnormal-looking moles or older changing moles, especially in patients with a history of significant sun exposure which includes burning. This will be more likely in those with red hair, blue eyes and lighter skin.

A past history or a family history of malignant melanoma means patients are at higher risk of developing it. At present, the only cure is early surgical excision, hence the importance of early referral. There is no curative role for chemotherapy or radiotherapy in malignant melanoma.

  • Dr Stollery is a GP in Kibworth, Leicestershire, and clinical assistant in dermatology at Leicester Royal Infirmary

Click here to take a test on this article and claim a certificate on MIMS Learning


  1. Cancer Research UK. Skin cancer mortality statistics.
  2. Cancer.Net. Familial malignant melanoma.

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