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How to Tell If a Mole Is Cancerous?

Firstly, don’t panic!

Even if the mole does turn out to be cancerous – provided action is taken early the outcomes are generally good.

The first thing to do before even looking at any individual mole is to work out in your mind how likely it is to be a ‘bad’ mole or melanoma skin cancer.

We do this by stacking up all of the things that might possibly make us more worried about melanoma skin cancer. There’s no hard and fast rule to this but the more worrying things there are in the story or ‘history’ that are present; the lower threshold for taking it out to check it under the microscope.

Cutting out moles to check them under a microscope is fairly straightforward but has it’s own risks and will leave a scar. An expert dermatologists opinion together with a good history and examination will help to prevent unnecessary procedures.

So, what are the things in the history are more concerning?

1. Having had melanoma skin cancer in the past

2. Melanoma skin cancer in a 1st degree relative

3. Large numbers of unusual looking moles

4. Previous moles that have been ‘active’ (dysplastic moles)

5. Periods of intense, intermittent sun-exposure (e.g. lots of foreign, sunny holidays)

6. Fair skin, blonde/redhead, burns easily

7. Blistering sunburn as a child

8. Living or working abroad in sunny climates

9. Spending lots of time outdoors (farming/gardening/military etc.)

10. Mole is new

11. Mole is changing/becoming darker/growing in size

12. Mole is itching/crusting/bleeding or ulcerating

Any of these features may cause your dermatologist to consider removing the mole to check it and make sure it is ok. If more than one of the above is present, or if it looks abnormal to them then the threshold for doing this would also be reduced. A decision will often be made in the doctor’s mind by this stage.

Next, they will want to look at the skin in generally and the mole itself and may also want to check to feel your lymph glands. There are various stages to this and often it is a more general, holistic process depending on ability.

The first step is to assess the skin overall and various questions (in no particular order) are considered by the doctor such as:

– Are there lots of moles overall?

– Does this mole look different to the others? (‘ugly duckling’ sign)

– Where is the mole? Is it on an area that gets lots of sun?

– Is the patient fair-skinned/blond or red-haired?

– Do they look like they might burn easily?

– Does the skin in general look like it has caught a lot of sun? Are there signs of photoaging?

– Are there any other areas that I’m worried about?

– Does the patient have any scars from moles that have been cut out before that they may have forgotten about?

– Do they look well/unwell?

– Are they tanned?

– What does the mole itself look like?

o Does the mole look symmetrical (good)? If you folded it in half would each half match the other?

o What do the edges look like? Are they regular (good) or irregular (more worrying) with lots of twists/turns

o Is the colour the same throughout the mole (good) or does it have darker areas or 2-3 colours within it (more worrying)

o How big is it? (moles >5-6mm are more concerning)

o Are there any hairs growing in it (generally good)?

– Are there any lumps or bumps in the lymph nodes that might show something has spread or raise the suspicion further.

In addition, moles that have been present many months unchanged are often more likely to be normal.

The next step is then to look at the mole under a dermatoscope (basically a magnifying glass and a light joined together). This is something that should be performed by an expert only as it can actually make things harder to interpret and cut accuracy in untrained hands.

The dermatoscope is very useful for confirming some features of both harmless and harmful pigmented lesions. It is particularly good at helping to show seborrhoeic keratoses (or seborrhoeic ‘warts’) which are completely harmless coloured ‘moles’ that nearly everybody gets with time. These can sometimes seem alarming to the untrained eye but clearly show a ‘greasy’, stuck on appearance with some characteristic features such as a ‘warty’ surface, pseudofollicular openings and milia-like cysts.

Harmful or worrying features under the dermatoscope include:

1. Assymetrical appearance or irregular border

2. Dark blobs/spots (particularly near the border)

3. Pseudopods (foot-like projections at the border)

4. Irregular pigment network

5. Blue-white ‘veil’ – a characteristic blue/white structure that appears when examined closely with a dermatoscope

6. Areas of ‘regression’ – where part of the mole appears to have disappeared or ‘resolved’.

7. Signs of ulceration, crusting or bleeding

8. Abnormal colour patterns.

Using a combination of all the above a decision is then made about whether to remove the mole or ‘watch and wait’. It is often helpful to have a baseline photograph of the problem regardless of whether a decision to remove it is taken or not.

Nothing in medicine is perfect and if there are any concerns at all then a decision may be made to remove the mole or to take a small sample (‘biopsy’) to confirm the first suspicions.

If you have any concerns about a mole at all (particularly with any of the above features) then it is best to have an expert health professional check it as soon as possible.



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