Describe Malignant Melanoma in detail.

The Concept

Malignant melanoma is a malignant tumour of melanocytes — the pigment-producing cells of the skin. Although it accounts for a minority of skin cancers, it is by far the most dangerous because it metastasises early and widely. Its incidence is rising, and it is strongly linked to ultraviolet (sun) exposure. The key to a good outcome is early recognition and excision before it invades deeply.

Risk Factors

Risk factors include ultraviolet exposure (especially intermittent intense exposure and sunburn), fair skin that burns easily, multiple or atypical (dysplastic) naevi, a family or personal history of melanoma, immunosuppression, and a giant congenital naevus.

Recognition — the Abcde Rule

A changing mole is assessed with the ABCDE criteria:

• A — Asymmetry
• B — Border irregularity
• C — Colour variation (several shades)
• D — Diameter > 6 mm
• E — Evolution (change in size, shape or colour)

Additional warning symptoms are itching, bleeding, crusting or ulceration of a pigmented lesion.

Types

The main subtypes are superficial spreading (commonest), nodular (aggressive, grows vertically early), lentigo maligna melanoma (on sun-damaged skin of the elderly face), and acral lentiginous (on palms, soles and under nails — the commonest type in darker-skinned people).

Prognosis & Spread

The single most important prognostic factor is the Breslow thickness — the depth of the tumour in millimetres (the deeper the tumour, the worse the prognosis); ulceration and mitotic rate also matter. Melanoma spreads by lymphatics (to regional nodes) and by blood, and is notorious for being able to metastasise to almost any organ (liver, lung, brain, bone), sometimes years later.

Investigation & Management

Diagnosis is by excision biopsy of the whole lesion (to allow accurate measurement of Breslow thickness), followed by staging (sentinel lymph node biopsy for staging, and CT/pet for advanced disease). Management is:

• Wide local excision — with the margin determined by the Breslow thickness.
• Sentinel lymph node biopsy to stage the nodal basin; lymph node dissection if involved.
• Advanced/metastatic disease — immunotherapy (checkpoint inhibitors such as pembrolizumab, nivolumab, ipilimumab) and, for BRAF-mutant tumours, targeted BRAF inhibitors (e.g. Vemurafenib).

Growth Phases & WHY Depth Matters

Understanding the two growth phases explains why Breslow thickness is so powerful a predictor. Melanoma initially grows in a radial (horizontal) phase, spreading within the epidermis (in situ) and superficial dermis, during which it has little metastatic potential. It then enters a vertical (invasive) phase, penetrating deeper into the dermis and gaining access to lymphatics and blood vessels — and hence the ability to metastasise. Since Breslow thickness measures exactly this depth of vertical invasion, it directly reflects the tumour's access to the routes of spread, which is why it dominates prognosis and dictates excision margins.

Staging & the Sentinel Node

Staging uses the TNM system, and the sentinel lymph node biopsy is a key concept: the 'sentinel' node is the first node draining the tumour's territory, identified using a dye and radioactive tracer. If this first node is free of tumour, the rest of the basin is very likely free too, sparing the patient a full dissection; if it contains tumour, it upstages the disease and guides further treatment. This elegant technique provides accurate staging with minimal morbidity.

The Revolution in Advanced Disease

Historically metastatic melanoma was almost untreatable, responding poorly to chemotherapy and radiotherapy. The management has been transformed by two developments: immune checkpoint inhibitors (anti-PD-1 agents such as pembrolizumab and nivolumab, and anti-CTLA-4 ipilimumab), which release the brakes on the immune system to attack the tumour; and targeted therapy with BRAF (and MEK) inhibitors for the roughly half of melanomas carrying a BRAF mutation. These have produced durable responses in a disease that was once rapidly fatal.

A Note on Amelanotic & Occult Melanoma

A clinical trap worth knowing is the amelanotic melanoma — a melanoma that produces little or no pigment and therefore appears as a pink or flesh-coloured nodule rather than a dark lesion, easily mistaken for something benign. Melanoma can also arise at hidden sites — under a nail (subungual), on the sole, in the eye (uveal melanoma), or on mucosal surfaces. Occasionally it presents first as a metastasis (e.g. An enlarged node) from an unknown or regressed primary. These atypical presentations are why any changing, atypical or unexplained lesion deserves careful assessment.

• ABCDE: Asymmetry, Border, Colour, Diameter >6 mm, Evolution.
• Breslow thickness (depth in mm) is the most important prognostic factor; excision biopsy for diagnosis.
• Wide local excision (margin by Breslow) + sentinel node biopsy; advanced → immunotherapy/BRAF inhibitors.

Breslow thickness is the single most important prognostic factor.

• Malignant melanoma = malignant tumour of melanocytes; most dangerous skin cancer (early, wide metastasis); UV-related.
• Recognise with ABCDE (Asymmetry, Border, Colour, Diameter >6 mm, Evolution) + itching/bleeding.
• Types: superficial spreading (commonest), nodular (aggressive), lentigo maligna, acral lentiginous (dark skin).
• Breslow thickness (depth) is the most important prognostic factor; diagnose by excision biopsy; can metastasise to any organ.
• Wide local excision (margin by depth) + sentinel node biopsy; advanced → immunotherapy (checkpoint inhibitors)/BRAF inhibitors.