Melanoma (Skin Cancer): Symptoms and Warning Signs

Melanoma is the most serious form of skin cancer. It develops from melanocytes, the pigment-producing cells of the skin. These cells normally make melanin, the pigment that gives skin its colour and offers some protection against ultraviolet light. When melanocytes turn cancerous and start to grow out of control, a melanoma can form, often, but by no means always, dark in colour. Melanoma differs from the more common non-melanoma skin cancers, such as basal cell and squamous cell carcinoma, in one crucial way. It is far more likely, and at an earlier stage, to spread to other parts of the body through the lymph and blood system. That tendency to spread is what makes it so dangerous. There is good news, and it is the whole reason for this article. When melanoma is found and removed early, while it is still thin and confined to the upper layers of the skin, the outlook is usually very good. The deeper the tumour has grown, the more serious the situation becomes. Knowing the warning signs is therefore not specialist knowledge; it is something everyone should be aware of. Rates of melanoma have risen markedly over recent decades. It is also one of the cancers that appears comparatively often in younger adults, so it is a mistake to think of it as a disease only of older age.

To tell a suspicious change from a harmless mole, doctors often use the ABCDE rule. It is a simple checklist that anyone can use for self-monitoring, with each letter standing for a feature worth a closer look. A is for asymmetry. A harmless mole is usually round or oval and roughly symmetrical, so that an imaginary line through the middle gives two matching halves. A mole that looks lopsided or irregular is an early warning sign. B is for border. Benign moles tend to have a smooth, clearly defined edge. Blurred, ragged, notched or poorly defined borders are more concerning. C is for colour. A worrying mole is often unevenly coloured, showing several shades within one spot, different browns and black, and sometimes red, blue, grey or unusually pale areas. D is for diameter. Moles larger than about six millimetres, roughly the width of a pencil eraser, deserve extra attention. Size alone is not proof, though, because small moles can also be cancerous. E is for evolving. Many experts consider this the single most important sign. Any change over weeks or months in size, shape, colour or thickness, or new symptoms such as itching, bleeding or crusting, should be checked by a doctor. Use the rule for what it is: a guide, not a diagnosis. Meeting one or more of the criteria does not automatically mean cancer, but it is a good reason to have the mole examined by a dermatologist or your GP.

The ABCDE rule covers many melanomas but not all of them. It is worth keeping a few extra warning signs in mind, which in everyday life are sometimes easier to notice than the individual letters. One useful idea is the "ugly duckling" sign. Most people have several moles that all look fairly similar. If one mole stands out from the rest because it simply looks different, that is suspicious. The human eye is surprisingly good at picking out the odd one out, often faster than a formal ABCDE check. Also take seriously any mole or patch of skin that itches, bleeds, weeps, crusts over or refuses to heal. A new dark spot appearing after the age of about 40 deserves attention too, since genuinely new benign moles rarely form at that age. None of these signs proves illness on its own. They are simply a reason to look more closely and, if in doubt, to book an appointment rather than wait and see.

A common misconception is that melanoma only develops where the sun reaches most often. In fact, melanomas can appear anywhere on the body, including areas that rarely see daylight. In men, melanoma is often found on the back; in women, frequently on the legs. Beyond that there are spots that are easy to forget during a self-check: the soles of the feet and palms of the hands, the skin under fingernails and toenails, the scalp beneath the hair, the ears, between the toes and the mucous membranes. In rare cases the eye can be affected too. A new dark streak running along a fingernail or toenail deserves special attention, as it can be a sign of acral lentiginous melanoma. This form occurs on the hands, feet and nails and also affects people with darker skin, in whom other types of melanoma are less common. When you examine your own skin, make a point of including these hidden areas rather than only the sun-exposed parts.

Melanoma is not a single, uniform disease. Doctors distinguish several main types that differ in appearance, growth pattern and where they tend to occur. This background helps explain why the warning signs can look so different from one case to another. Superficial spreading melanoma is the most common type. It first grows outwards, spreading flat across the upper layer of skin before moving deeper. As a result it is often visible for some time as a flat, irregular patch. Nodular melanoma is considered particularly aggressive. It grows quickly and deep early on, often appearing as a raised, dark lump that may bleed. Because it skips the typical flat phase, it does not always fit the ABCDE rule neatly, which makes watching for change all the more important. Lentigo maligna melanoma tends to develop on skin with long-term sun damage, such as the face of older people, and usually grows slowly. Acral lentiginous melanoma appears on the hands, feet and nails. This variety shows that there is no single typical look, which is why any unusual, and above all any changing, area should be taken seriously.

Anyone can develop melanoma, but certain factors raise the risk. Knowing them helps you take sensible precautions and pay closer attention to your skin. The most important factor you can influence is ultraviolet radiation, from the sun and from sunbeds. Severe sunburn in childhood and adolescence is thought to matter especially. The World Health Organization classes the UV radiation from sunbeds as cancer-causing to humans, so avoiding sunbeds is one of the simplest ways to protect your skin. Other factors are down to individual make-up and cannot be changed. Risk is higher for people with fair skin that burns easily and rarely tans, often with freckles, red or blond hair and light-coloured eyes. Having a large number of moles, or moles that look unusual and irregular, also increases risk. On top of this come a family history of melanoma, a previous skin cancer of your own, and a long-term weakened immune system, for example after an organ transplant. If several of these apply to you, it is worth having your skin checked especially regularly.

Looking over your own skin regularly takes little time and is one of the most effective forms of early detection. Many melanomas are first noticed by the person affected or by someone close to them. Check your skin in good light and work through it systematically from head to toe, including hard-to-see areas such as the back, scalp, soles of the feet and between the toes. A second mirror or a partner's help makes the back easier to inspect. Photographs of any unusual moles help you spot changes over time. Unlike some countries, the UK does not run a routine national skin screening programme, so day-to-day self-checks and prompt attention to changes are all the more important. If you are at higher risk, your GP can advise on monitoring. Do not wait until a routine appointment if a mole changes quickly, bleeds, itches or weeps, if a patch fails to heal over several weeks, or if a new, unusual mole appears. When in doubt, it is better to have something looked at once too often than to ignore a change for too long.

This article is for general information only and to support early detection. It is meant to help you make sense of warning signs and seek medical advice at the right moment. It does not replace a medical examination, consultation or diagnosis. Whether a skin change is harmless or needs treatment can only be judged reliably by a doctor, usually with a dermatoscope and, if needed, a tissue sample. Digital tools such as DermCheck are intended to support self-monitoring and give a first orientation, not a diagnosis. If you are unsure or notice a change, please contact a dermatologist or your GP.