Melanoma — the complete guide

Melanoma is one of the most dangerous skin cancers — yet also one of the most treatable, provided it is caught early. This guide brings the essentials together in one place: what melanoma is, who is most at risk, how to recognise worrying changes, and how regular skin monitoring can save a life. Each section is a short introduction with a link to a separate, in-depth article. Keep in mind, though, that no text or app can replace an examination by a dermatologist — this is educational material, not a diagnosis.

What is melanoma?

Melanoma develops from melanocytes — the skin cells that produce pigment (melanin), which gives skin its colour and helps protect it from UV radiation. When melanocytes begin to divide uncontrollably, a malignant tumour forms. It can appear within an existing mole or as a completely new lesion on previously clear skin.

What makes melanoma dangerous is its ability to spread (metastasise) — cancer cells can penetrate deeper into the skin early on and travel to lymph nodes and other organs. That is why time matters: melanoma found at an early stage, before it grows deep, has a very good prognosis. The encouraging part is that melanoma develops on the surface of the skin, which you can watch yourself.

Risk factors — who should be careful?

Melanoma can affect anyone, but certain features raise the risk. The more of them apply to you, the more attention your skin deserves:

• Fair skin — skin that burns easily and tans poorly, light or red hair, freckles, light eyes
• Many moles — especially a high total number, and the presence of atypical (dysplastic) moles
• Past sunburns — particularly severe, blistering burns, especially in childhood
• Tanning-bed use — artificial UV markedly raises the risk, especially in younger people
• Melanoma in the family, or a melanoma you have had before
• Weakened immunity — for example after a transplant or during immunosuppressive therapy

An absence of risk factors does not mean you are completely safe — melanoma also occurs in people with darker skin and in areas not exposed to the sun (palms, soles, under the nails). That is why self-examination is worthwhile regardless of your risk profile.

How to recognise melanoma — the ABCDE rule

The simplest tool for an initial assessment of a mole is the ABCDE rule. Each letter describes one feature you can see with the naked eye:

• A — Asymmetry: the two halves of the mole differ
• B — Border: irregular, ragged, blurred, or notched
• C — Colour: several different shades within one lesion
• D — Diameter: classically over 6 mm, though melanomas can be smaller
• E — Evolution: any change over time — the single most important sign

This is a screening method, not a diagnostic one — it helps you decide which mole to show a doctor. For a full walk-through of all five criteria, with practical examples, see the dedicated guide: how to assess a mole using the ABCDE rule.

What melanoma looks like and its early signs

Early melanoma most often looks like a flat or slightly raised patch that stands out from the surrounding skin and your other moles. It is easily mistaken for an ordinary mole. Importantly, early melanoma usually does not hurt or itch, so the absence of symptoms does not mean a lesion is harmless.

It is worth knowing that melanoma is not always dark. There is amelanotic melanoma, which looks like a pink or red bump, and nodular melanoma — a fast-growing, firm lump that can bleed. A separate form develops on the palms, soles, and under the nails. You will find a detailed description of the different appearances of melanoma and its first signs here: what melanoma looks like — the first signs.

Types of moles — which are normal?

The vast majority of moles on the body are completely harmless. We have moles that are congenital and acquired, flat and raised, light and dark — and all of these variants can be perfectly normal. The key is being able to tell a typical mole from a lesion that needs attention.

A special group is atypical (dysplastic) moles — larger, with an irregular shape and uneven colour. They are not melanoma in themselves, but their presence can indicate higher risk and signal a need for closer observation. To learn to tell the different types of moles apart, read: types of moles and how to recognise them.

Skin self-examination — your first line of defence

Regular self-examination is the simplest and cheapest way to catch a worrying change early. It means systematically looking over all your skin — from head to feet — in good light, using a mirror for hard-to-reach spots or asking someone close to help. Do not forget the easily missed areas: the scalp, back, buttocks, between the fingers and toes, the soles of the feet, and around the nails.

The aim of self-examination is to learn the "map" of your own skin, so you notice when something changes or a new lesion appears. You will find a full step-by-step guide in the article: skin self-examination step by step.

How often to monitor and photograph your moles?

A single self-exam shows the situation today — but melanoma reveals itself above all through change over time. That is why regularity and documentation matter so much. For most people a sensible rhythm is a self-exam once a month and photos of the moles you watch every 3–6 months, more often if something raises doubt or you are in a higher-risk group.

Photos taken under similar conditions (daylight, the same distance, a scale reference) let you compare a mole "before and after" reliably. To learn how to set the right rhythm and how to photograph so the images are comparable, read here: how often to photograph your moles.

Prevention and sun protection

The most important modifiable risk factor for melanoma is UV radiation — from both the sun and tanning beds. The good news is that you can reduce a large part of the risk with simple habits:

• Avoid the sun during peak hours (usually around midday)
• Use a high-SPF sunscreen (SPF 30–50+) and reapply it every few hours
• Wear protective clothing, a hat, and sunglasses
• Protect children especially — childhood burns have long-term effects
• Give up tanning beds

Sun protection does not mean avoiding the sun entirely — it is about common sense and avoiding burns. You will find detailed advice on choosing sunscreens and everyday protection in the article: melanoma prevention and sun protection.

When to see a dermatologist and what is dermoscopy?

Do not wait for your next monitoring session if you notice a mole that bleeds without injury, itches or hurts, grows quickly, clearly stands out from the rest (the so-called ugly duckling), or meets several ABCDE criteria. A dark, widening streak under a nail also calls for a consultation.

During the visit, the dermatologist examines lesions with a dermatoscope — a device that magnifies a mole several times and reveals structures invisible to the naked eye. It is a non-invasive, painless examination. If there is any doubt, the doctor may recommend removing the lesion for histopathological analysis. What happens during such a visit and when to go is described here: when to see a dermatologist and what dermoscopy is.

It is better to show a doctor a harmless lesion one time too many than to miss a melanoma one time too few. Early detection saves lives.

How J-Skin helps you monitor your moles

J-Skin is a tool for systematic skin monitoring, designed with privacy in mind — your photos and data stay on your device. The app helps you do what is hardest with the naked eye: catch slow change over time:

• Body map — you mark the location of each mole and keep a separate history for it
• Photos over time — a "ghost" overlay helps you line up the new photo exactly over the previous one, and four comparison modes show the differences
• Measurement in millimetres — with coin calibration the app calculates the real size, so you see actual growth rather than a trick of perspective
• ABCDE module — walks you through each criterion of appearance
• Reminders — regular sessions every 3–6 months, set individually for each mole
• PDF report — take your photo and measurement history with you to the dermatologist

J-Skin does not make a diagnosis and does not replace a doctor — it is an observation tool that helps you notice when it is worth getting checked. The decision about diagnosis and treatment is always made by a specialist.

This article is for educational purposes only and does not replace a consultation with a dermatologist. Any worrying or changing skin lesion needs to be assessed by a doctor.