Melanoma !
Melanoma is a skin cancer that starts in pigment cells. It is less common than other skin cancers but spreads early, so a changing mole matters.
Updated 2026-11-01
Structures involved
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In the clinical exam
Why it happens
- Invasion and metastasis: the metastatic cascade, step by step
- Oncogenes: RAS, MYC, HER2, BCR-ABL and the table to know
- How tumours evade the immune system
- Radiation and cancer: ultraviolet and ionizing
- Biopsy: excisional, incisional, core needle, punch and fine-needle aspiration
- Naming tumours: -oma, carcinoma, sarcoma, and the misleading names
Show 13 more
- The cell cycle in cancer: cyclins, CDKs and checkpoints
- From specimen to report: fixation, margins and the pathology report
- Frozen section: the intraoperative consultation
- Immunohistochemistry: the principle and the markers to know
- Molecular pathology: PCR, FISH, sequencing and liquid biopsy
- The hallmarks of cancer
- Evading cell death and replicating without limit: BCL2 and telomerase
- Pathways of spread and the usual metastatic sites
- Tumour suppressor genes: RB, TP53, APC, BRCA and the two-hit hypothesis
- Ionizing radiation injury
- Genomic instability: mismatch repair, BRCA and xeroderma pigmentosum
- Tumour markers: serum and tissue, and what each one is for
- Keratinocytes, melanocytes, Langerhans and Merkel cells
What it is
A malignant tumour of melanocytes, the pigment-producing cells of the skin (and, less often, of the eye and mucosae). It causes most skin-cancer deaths because it can metastasise through lymphatics and blood while still small.
Who gets it
Less frequent than basal and squamous cell carcinoma but responsible for most skin-cancer mortality. In Colombia and Latin America the Andean altitude raises UV exposure, and in people with darker skin the acral lentiginous type (palms, soles, under the nails) makes up a larger share of cases and is often diagnosed late.
Causes
- Ultraviolet damage to melanocyte DNA, especially intermittent intense exposure and sunburns
- Driver mutations in the MAPK pathway (BRAF, NRAS) and loss of tumour-suppressor genes
- Inherited susceptibility in some families (e.g. CDKN2A mutations)
Risk factors
- Fair skin, light eyes, red or blond hair and tendency to burn
- History of blistering sunburns, especially in childhood, and use of tanning beds
- Many common moles or atypical (dysplastic) naevi
- Personal or family history of melanoma
- Immunosuppression
- Large congenital naevus
Pathophysiology
Mutated melanocytes first spread sideways within the epidermis (radial growth phase), when excision is usually curative. Once they invade down into the dermis (vertical growth phase) they reach lymphatics and blood vessels, so tumour thickness (Breslow depth) is the strongest predictor of nodal and distant spread.
Classification
- Superficial spreading: the most common type worldwide; flat, irregular, on the trunk or legs
- Nodular: raised, grows down quickly, often thick at diagnosis
- Lentigo maligna: slow-growing on chronically sun-damaged facial skin of older adults
- Acral lentiginous: palms, soles and nail beds; relatively more common in darker-skinned and Latin American patients
- Staging (TNM) by Breslow thickness, ulceration, lymph-node status and distant metastases
Symptoms and signs
- A new pigmented spot or a mole that changes (ABCDE: asymmetry, irregular border, uneven colour, diameter usually over 6 mm, evolution)
- A mole that looks different from the person's other moles (the ugly duckling sign)
- Itching, bleeding or crusting of a pigmented lesion
- A dark streak along the nail (longitudinal melanonychia), sometimes with pigment spreading to the nail fold (Hutchinson sign)
- A dark, irregular patch on the sole or palm that was mistaken for a bruise or wart
Diagnosis
- Clinical
- Full skin examination including scalp, palms, soles, nails and mucosae, with the ABCDE rule and the ugly duckling sign; dermoscopy improves accuracy. Regional lymph nodes are palpated.
- Tests
- Excisional biopsy with narrow margins is preferred so that the pathologist can measure Breslow thickness and ulceration; shave biopsy that cuts through the lesion is avoided. Sentinel lymph node biopsy is offered for thicker or ulcerated tumours. Molecular testing (e.g. BRAF) in advanced disease; LDH has prognostic value in metastatic disease.
- Imaging
- Not needed for thin melanoma. Ultrasound of regional nodes, and CT, PET-CT or brain MRI for staging when disease is advanced.
Differential diagnosis
- Benign melanocytic naevus or atypical naevus
- Seborrhoeic keratosis
- Pigmented basal cell carcinoma
- Subungual haematoma (for nail lesions)
- Plantar wart or haemangioma
Goal of treatment
Remove the primary tumour completely with the right margin for its thickness, stage the lymph nodes, and in advanced disease control spread and prolong survival.
Treatment
- Surgical
- Wide local excision with margins chosen by Breslow depth is the main treatment for primary melanoma; for subungual or acral tumours this may mean partial digital amputation.
- Surgical
- Sentinel lymph node biopsy for staging in selected tumours; lymph-node dissection or nodal surveillance when nodes are involved.
- Medical
- Immunotherapy with immune checkpoint inhibitors (anti-PD-1, anti-CTLA-4) and, for BRAF-mutated tumours, targeted BRAF and MEK inhibitors, used for advanced disease and as adjuvant therapy after surgery in higher-risk stages.
- Procedure
- Radiotherapy for selected brain, bone or unresectable metastases.
- Follow-up
- Regular full skin and lymph-node examinations and, in higher stages, imaging during follow-up; teaching self-examination.
Drugs for this condition
Complications
- Lymph-node metastases
- Distant metastases to lung, liver, brain and bone
- Local recurrence and in-transit metastases
- Second primary melanoma
- Lymphoedema after lymph-node surgery
Prognosis
Excellent for thin melanoma removed early; survival falls with greater Breslow thickness, ulceration and nodal spread. Modern immunotherapy and targeted therapy have markedly improved survival in metastatic disease. Acral melanoma tends to have a worse outcome mainly because it is found later.
Prevention
- Sun protection: shade, protective clothing, hats and broad-spectrum sunscreen; avoiding sunburn and tanning beds
- Skin self-examination, including soles, palms and nails
- Periodic professional examination of people at high risk
Test yourself
Think of the answer, then tap the question to see it.
What does the ABCDE rule for melanoma stand for?
Asymmetry, Border irregularity, Colour variation, Diameter (usually over 6 mm) and Evolution (change over time).
Which single feature of the primary tumour best predicts prognosis in localised melanoma?
Breslow thickness (depth of invasion measured in millimetres), together with ulceration.
Which melanoma subtype affects palms, soles and nail beds and is relatively common in darker-skinned Latin American patients?
Acral lentiginous melanoma.
Why is excisional biopsy preferred over a superficial shave for a suspected melanoma?
It removes the whole lesion so the pathologist can measure full thickness and ulceration for staging.
What is the purpose of sentinel lymph node biopsy in melanoma?
To stage the regional nodes by sampling the first draining node; its result guides further nodal treatment and adjuvant therapy.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Melanoma (MedlinePlus, US National Library of Medicine, 2026); Melanoma Treatment (PDQ®)–Patient Version (National Cancer Institute, 2026).
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