Moles: are they harmless or should the doctor take a look?


Distinguishing dangerous moles from harmless skin changes can sometimes be difficult. Here we explain how to recognise melanoma and non-melanoma skin cancer and when it’s advisable to see a doctor.

Recognising when a mole is dangerous

First things first: not all dark spots on the skin are a reason to worry. Moles, also called liver spots, are usually no cause for concern. Nevertheless, in rare cases they can develop into malignant melanoma. This is particularly dangerous because melanoma can form metastases.

The quick home test: the ABCD rule

If you're unsure, you can check your moles – or those of your partner – with a quick test at home.

A = Asymmetry: is the shape of the mole irregular?
B = Borders: are the edges blurred or jagged?
C = Colours: is the mole more than one colour? Does it have a brown, black, grey, red, purple or white sheen?
D = Dynamics: has the mole changed in shape or colour?

Examination by a doctor

If any of the above applies, a medical examination is advisable. The same applies if the mole itches, waters, bleeds or forms a crust. Regular check-ups are especially important for risk group patients. These are people:

  • with over 100 moles on their body
  • who have had skin cancer before or have a family history
  • with a weakened immune system

Removing moles

If malignant moles are discovered early, the chances of a cure are good. An operation is performed to cut out the melanoma, and also the healthy skin around it to make sure that all cancer cells are removed. In these cases, relapses are rare. Nevertheless, it's important to go for regular follow-up checks.

Recognising non-melanoma skin cancer

Moles resulting from non-melanoma skin cancer are usually also surgically removed. Very superficial forms (see actinic keratosis) can often be treated with a special cream, freezing or light therapy. In the early stages, non-melanoma skin cancer is easily curable.

Basal cell carcinoma

  • This originates in the basal cell layer of the epidermis and is mostly found in parts of the body that are heavily exposed to sunlight: scalp, bald head, forehead, nose, lips, ear rims, back of the foot or hand.
  • Basal cell carcinomas grow slowly. They present in the form of changes to the skin that can vary and may include: a hardening of the skin, edges that resemble a string of pearls, dilated blood vessels or small craters. Basal cell carcinomas can be brownish or yellowish in colour and have a glassy-white sheen. They can also form a crust, or bleed.
  • Basal cell carcinomas almost never form metastases, but sometimes reappear in the same or other parts of the body after treatment. If left untreated, this form of cancer can grow in size and in depth, and destroy tissue as well as bone and cartilage.

Squamous cell carcinoma

  • This type of cancer develops in the squamous cells of the epidermis and is the result of chronic skin damage, often caused by UV rays. Squamous cell carcinomas are therefore also frequently found on the parts of the body most exposed to sunlight.
  • Typical signs: slowly growing nodules that harden and become encrusted over time. Sometimes weeping or bleeding wounds form.
  • Squamous cell carcinomas can form metastases, so early detection is important.

Actinic keratosis

  • This is a form of precancer. It develops from the squamous cells of the epidermis and also appears on sun-exposed parts of the body. It is often found on men with a bald head, and has a speckled look.
  • Typical signs: pink-coloured, reddish or brownish spots or nodules with a scaly or rough surface.
  • If actinic keratosis is detected and removed in time, it cannot develop into non-melanoma skin cancer.

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