How to Know if a Mole is Dangerous

Do you have any concerns about a mole? Here are 7 criteria that should alert you to the danger of a mole.
How to Know if a Mole is Dangerous
Diego Pereira

Reviewed and approved by el médico Diego Pereira.

Last update: 14 March, 2023

Moles are small colored spots that develop on the skin. Most of them appear during childhood, although they can continue to appear until the second decade of life. They are benign growths of skin cells, and their changes can alert us to the development of a melanoma. We’ll show you 7 ways to know if a mole is dangerous.

Keep in mind that this explanation is not a substitute for the opinion of a professional. If you have a suspicious mole, then consult a specialist, even if it doesn’t have any of the following signs. Do this especially if you have a history of melanomas in your family history.

7 signs that a mole is dangerous

As indicated by the American Cancer Society, the ABCDE rule is an effective guide to watch out for melanoma symptoms. The rule consists of the following:

  • A for asymmetry
  • B for border
  • C for color
  • D for diameter
  • E for evolution

Although it may seem like a simple guide, the truth is that it’s a quick, effective, and practical way to know if a mole is dangerous. In the following lines we’ll expand on these and explain things to you so you can understand them easily.

1. It has gotten bigger

A dangerous mole increases a lot in size
Changes in the size of moles are often the first changes noted in a self-assessment.

As the experts point out, the enlargement of the mole is one of the main indicators that a mole is dangerous. In general, the size isn’t a sign of melanoma. Most moles are no larger than 6 millimeters, but even the ones that are bigger may well be benign moles. However, it’s a different story if the mole has increased in size in a matter of days, weeks, or months.

It’s important to keep in mind that benign moles don’t change in size. They shouldn’t get smaller, nor should they get bigger. This rule of course does not apply to those who are growing (young people and adolescents) or who have gained or lost a lot of weight. Certainly, stretching or shrinking the skin can create the sensation that they have changed in size.

2. It has changed shape

Another way to know if a mole is dangerous according to researchers is if it changes its shape. Although, of course, we find exceptions, most moles are oval or round. The criterion that you must take into account is that of asymmetry. Draw an imaginary line in the middle of the mole, and see if the two parts are similar to each other.

Almost all moles are symmetrical, and many asymmetrical moles are malignant. Naturally, the two parts won’t agree 100%, but when they’re very different from each other they should raise suspicions. When assessing its shape, take into account the criteria of asymmetry and irregularity.

3. It has changed color

Most moles are brown in color, but they can range from light brown to deep black. Because the spectrum is broad they may appear to be pink in color or even take on a bluish hue in the light. Apart from this, the important thing is that its color is stable with no different color tones.

Therefore, changes in its tone or several different shades in a single mole should never go unnoticed. For example, changing from light brown to black or if it has one part dark and another part light. This is a way of telling that a mole is dangerous, especially if the asymmetry has changed.

4. It itches or hurts

Although not all malignant moles have this symptom, many of them tend to be itchy or painful. This sign occurs regardless of external factors, such as friction with clothing or interaction with irritating agents. Moles should not cause you pain, itching, tingling, or any other change in sensation.

5. Has developed texture change

A dangerous mole has texture changes.
Rapidly appearing texture changes should alert to the presence of a suspicious lesion.

The presence of changes in relief is another warning sign to know if a mole is dangerous. It’s true that some may have a rough surface, but it isn’t normal for a previously smooth one to change its texture. If this change has occurred recently, you should treat it as a warning.

6. You experience bleeding in the mole

Again, this is a symptom that doesn’t always manifest occur, but one that you should still be aware of. The scabbing added to the itching can make you scratch especially hard. This can lead to slight bleeding, although this can appear regardless of friction. It’s a sign that usually develops in the most acute stages of melanoma.

7. Comparison with other moles

Some call this the ugly duckling rule. It’s a strategy in which you compare the mole with others that you have on your body.

In general, most moles look similar to each other. They are similar in size, color, and shape. If when comparing the suspicious mole with other moles you discover that it’s very different, then you should take note. In these cases, it’s advisable to consult a professional.

It’s important to check frequently

Remember that not all malignant moles fit these signs. Other signs to tell if a mole is malignant are lumps or bumps, sores that won’t heal, the spread of pigment into the surrounding skin (with a lighter shade), redness at the edge of the mole, and tenderness.

As we have already told you, the best thing you can do is consult a professional. Do this when you notice a skin abnormality, whether or not it meets the above criteria.

The American Academy of Dermatology points out that those who have atypical moles, who have already had melanoma in the past, or who have a first-degree relative who has suffered from the complication should be more attentive to the signs.

  • Heistein, J. B., & Acharya, U. (2021). Malignant Melanoma. 2021.
  • McCourt, C., Dolan, O., Gormley, G. (2014). Malignant melanoma: a pictorial review. Ulster Med J;83(2):103-110.

Este texto se ofrece únicamente con propósitos informativos y no reemplaza la consulta con un profesional. Ante dudas, consulta a tu especialista.