Doctor examining a patient's skin during a medical office.

How to tell the difference between a normal mole and a possible melanoma

Spotting the appearance of new moles, or any changes in existing ones, as soon as possible is essential to detect melanoma in its early stages

BY María Pérez | 25 June 2025

Summer is coming and, as every year, exposure to the sun is once again an important issue. Spending more time outdoors means increased exposure to ultraviolet rays, which can have direct effects on our skin. In this context, it is important to remember that moles can increase in number or change in appearance with solar radiation. The skin, our largest and most visible organ, deserves constant attention; being alert to any changes in its appearance is not only a matter of aesthetics, but also of health. Melanoma can be mistaken for a common mole, so learning to distinguish it is essential for early detection and effective treatment.

What is melanoma?

Melanoma is the most aggressive form of skin cancer. It originates in melanocytes - the cells responsible for producing melanin - and most often appears on areas of the skin which have been exposed to the sun. Often, the first warning sign is the presence of a mole that is unusual in colour, shape and size. In its early stages, melanoma remains limited to the most superficial layers, but if not detected in time it can reach into the dermis and metastasise. There are different types of melanoma, and superficial spreading melanoma (SSM) is the most common; it is characterised by a flat lesion that usually appears on the arms, legs or torso.

The ABCDE of melanomas

To tell a melanoma apart from a common mole, we should use the ABCDE mnemonic rule. There is no need for all these factors to be present; in many cases, spotting just one of these changes is enough to seek medical advice.

A: asymmetry. Melanomas often have one side that is different from the other. Drawing an imaginary line across the nevus, we should compare the two halves to assess whether there is asymmetry.
B: irregular borders. Benign moles usually have a smooth, even border, in contrast to melanomas, whose outline is often jagged, blurred and poorly defined.
C: uneven colour. Melanomas usually include more than one colour (black, blue, brown, white, red, beige, etc.), unlike normal moles, which are characterised by a homogeneous brown colour. An uneven distribution of colours can also be a warning sign.
D: diameter. Melanomas are usually larger in diameter than benign moles. A nevus larger than 6 mm should be a cause for concern.
E: evolution. Any change in the shape and size of a mole, as well as the appearance of itching or bleeding, can be symptoms of the presence of malignant cells.

Ultimately, being aware of the risk factors, protecting the skin from the sun and applying the ABCDE rule to self-assess our moles will give us a decisive advantage: early detection. If there is the slightest suspicion, consulting a dermatologist can prevent a localised problem from becoming a risk for the whole body. Prevention is within everyone's reach; taking care of our skin today is an investment in the future of our health.