Conditions: Melanoma of The Skin

(Cutaneous Melanoma)

Melanoma is a cancer of the skin's pigment-producing cells that is less common than other skin cancers but more likely to spread.

What is melanoma?

Melanoma is a cancer that begins in the pigment-producing cells of the skin called melanocytes. These cells sit in the deepest part of the outer skin layer (the epidermis) and make melanin, the pigment that gives skin, hair, and eyes their color and that helps shield the skin from ultraviolet (UV) light. When a melanocyte's DNA is damaged and the cell begins to grow out of control, a melanoma can form.

Melanoma is far less common than the other main skin cancers (basal cell carcinoma and squamous cell carcinoma), but it is more likely to grow into deeper tissue and spread to other parts of the body, which is why early detection matters so much. Most melanomas arise on the skin (cutaneous melanoma). Because melanocytes are also found in the eye and on moist inner surfaces of the body, rarer forms can begin in the eye (uveal melanoma) or on mucous membranes (mucosal melanoma).

Why does the head and neck deserve special attention?

The head and neck are among the most heavily and chronically sun-exposed areas of the body, so melanomas in these locations are common and have some distinctive features. Melanomas on the face, ears, scalp, and neck of older adults are frequently linked to a lifetime of accumulated sun damage. Certain subtypes, particularly lentigo maligna melanoma and desmoplastic melanoma, arise disproportionately in these chronically sun-damaged areas. Melanomas of the scalp and neck can also be harder to notice (hidden by hair) and tend to carry a somewhat less favorable outlook than melanomas elsewhere.

What are the main types of melanoma?

Melanoma is not a single disease. The most common types include:

• Superficial spreading melanoma: the most common type (roughly 70% of cases). It usually grows outward along the skin surface for a period before growing downward, often appearing as a flat or slightly raised patch with irregular borders and mixed colors. It is linked to intermittent, intense sun exposure and often appears on the trunk or limbs, frequently in younger and middle-aged adults.

• Nodular melanoma: a raised, firm, dome-shaped bump that tends to grow downward quickly from the start. It may be dark, but can also be reddish or lack color, and it may bleed or crust. Because it grows fast, it accounts for a large share of serious cases. It commonly occurs on the trunk, head, or neck.

• Lentigo maligna melanoma: typically found on the chronically sun-damaged skin of the face and neck in older adults. It often begins as a slowly enlarging, flat, tan-to-brown patch (lentigo maligna) that may be present for years before it begins to invade more deeply.

• Acral lentiginous melanoma: occurs on the palms, soles, and under the nails. It is not strongly related to sun exposure and is the type most often seen in people with darker skin tones. Because these areas are easy to overlook, it is sometimes found late.

• Desmoplastic melanoma: an uncommon type that usually develops in severely sun-damaged skin of the head and neck in older people. It can be firm and often lacks the typical dark color, which makes it easy to mistake for a scar or a harmless bump and difficult to diagnose.

Some melanomas produce little or no pigment (amelanotic melanoma) and appear pink, red, or skin-colored; nodular, desmoplastic, and acral melanomas are more likely to lack pigment.

What are the risk factors for melanoma?

Several factors increase the chance of developing melanoma:

• Ultraviolet (UV) light exposure: the single most important preventable cause. Both sunlight and a history of sunburns, especially blistering sunburns and sunburns in childhood, raise risk. UV exposure is thought to contribute to the large majority of melanomas.

• Tanning beds and other indoor tanning devices: classified as cancer-causing to humans; the risk is higher with a start at a young age and with frequent use.

• Fair skin and related features: skin that burns rather than tans, red or blond hair, light-colored eyes, and a tendency to freckle. Melanoma can still occur in people with darker skin, often on the palms, soles, or nails and in areas not exposed to the sun.

• Many moles or atypical (unusual) moles: a high number of moles, or moles that are large or irregular in shape and color, substantially raises risk.

• Personal or family history: a prior melanoma or a close blood relative with melanoma increases risk. A minority of cases run in families through inherited gene changes.

• A weakened immune system: for example, after an organ transplant, with certain blood cancers, or with HIV/AIDS.

• Older age and male sex, as well as living in sunnier climates closer to the equator.

What does a melanoma look like?

Melanomas vary widely in appearance, and two approaches are commonly used to recognize a suspicious spot: the ABCDE rule (listed below) and the "ugly duckling" sign. Most of a person's moles tend to resemble one another, and a melanoma is often the "odd one out" that looks clearly different from its neighbors. Not every melanoma follows the ABCDE rules; nodular, desmoplastic, and colorless melanomas in particular may not. A spot that is new, changing, bleeding, itching, or simply different from the rest is the kind of finding that typically prompts a biopsy.

How is a melanoma diagnosed?

A skin examination, sometimes aided by a handheld magnifying device called a dermatoscope, is the first step, but a suspicious spot cannot be confirmed by looking alone. The diagnosis requires a biopsy, in which the lesion is removed (or sampled) and examined under a microscope by a specialist (see punch biopsy and pathology). Whenever possible, the goal is to remove the entire lesion with a narrow margin so that the full depth of the melanoma can be measured accurately. Very superficial "shave" sampling is generally discouraged for suspected melanoma because it may not capture the true depth. For large lesions or those in delicate areas such as the face or ear, a full-thickness sample of the thickest-looking part may be taken instead.

What other information does a biopsy provide?

If melanoma is confirmed, the pathologist reports several features that describe how advanced and how aggressive the tumor is. Key items include:

• Breslow thickness: a measurement, in millimeters, of how deeply the melanoma extends into the skin. This is the single most important predictor of outcome for melanoma that has not spread; thinner tumors have a much better outlook than thicker ones.

• Ulceration: whether the skin surface over the tumor has broken down. Its presence signals a more aggressive tumor and worsens the outlook at any given thickness.

• Mitotic rate: a count of how many tumor cells are actively dividing. A higher rate reflects a faster-growing tumor and is an important clue across all thicknesses.

• Satellite and microsatellite lesions: small deposits of melanoma cells separated from the main tumor. Their presence indicates that the cancer has begun to spread through nearby lymphatic channels and places the disease in a more advanced category.

Reports often also note growth beyond the margins, whether cancer has entered small blood or lymph vessels (lymphovascular invasion), whether it involves nerves (neurotropism), and the specific melanoma subtype.

How is melanoma staged, and what does stage mean for outlook?

Staging describes how far the melanoma has progressed and is the strongest guide to prognosis. It combines three pieces of information (the "TNM" system):

• T (tumor): thickness and ulceration of the primary melanoma.

• N (nodes): whether melanoma has reached nearby (regional) lymph nodes or the lymphatic channels leading to them.

• M (metastasis): whether melanoma has spread to distant organs.

In broad terms:

• Stage 0 (melanoma in situ): confined to the top layer of skin; it has essentially no ability to spread and is highly curable with surgery.

• Stages I and II: invasive melanoma still limited to the original site, with no lymph node or distant spread. Higher numbers within these stages reflect greater thickness and/or ulceration.

• Stage III: melanoma has spread to regional lymph nodes or to nearby skin or lymphatic channels (satellite or in-transit deposits).

• Stage IV: melanoma has spread to distant sites such as distant skin, lymph nodes, lungs, liver, brain, or other organs.

Two developments most strongly worsen the outlook: spread to lymph nodes (which moves the disease to stage III) and spread to distant organs (stage IV). Blood tests such as lactate dehydrogenase (LDH) may add prognostic information in advanced disease.

When is imaging necessary?

For thin, early melanomas without symptoms, routine scans are generally not needed and can produce misleading results. Imaging, such as CT, PET-CT, or MRI (sometimes including the brain), is typically reserved for higher-risk or more advanced melanoma, to look for spread before treatment, or to investigate specific symptoms.

What is sentinel node biopsy? When and why is it performed?

Sentinel lymph node biopsy (SLNB) is the main tool for checking whether a melanoma has quietly begun to spread to lymph nodes in people who have no obviously enlarged nodes. A harmless tracer (and often a blue dye) is injected around the tumor site to map which lymph node the area drains to first, the "sentinel" node. That node is removed and examined under the microscope. This is generally discussed for melanomas that are ulcerated or about 0.8 mm thick or greater. Finding melanoma in the sentinel node upstages the disease and helps guide decisions about further treatment and monitoring, although the procedure itself is a staging test rather than a cure. In the head and neck, lymphatic drainage can be complex, so specialized imaging (such as SPECT/CT) is sometimes used to pinpoint the sentinel node.

What is the typical survival by stage?

Outlook depends heavily on the stage at diagnosis, and modern therapies continue to improve these numbers. Most melanomas, roughly three-quarters, are found while still confined to the original site, when the outlook is excellent. As a general guide based on recent data:

• Early, localized melanoma (stage I): 10-year melanoma-specific survival of roughly 94% to 98%.

• Thicker localized melanoma (stage II): roughly 75% to 88% at 10 years, decreasing with greater thickness and ulceration.

• Lymph node or regional spread (stage III): a wide range, roughly 60% to 88% at 10 years depending on the extent of nodal involvement, and lower (around 24%) in the most advanced stage III category.

• Distant spread (stage IV): historically much lower, but greatly improved with modern immunotherapy; in recent trials, about 4 in 10 patients treated with combination immunotherapy were alive at 10 years.

These figures are population averages and cannot predict any one person's outcome, which depends on the specific features of the melanoma, overall health, and response to treatment. Melanoma found while still confined to the skin has the most favorable outlook.

Treatment in brief

Treatment is tailored to the stage. Surgery to remove the melanoma with an appropriate margin of normal-looking skin is the foundation of care for melanoma that has not spread and cures most early cases. For select facial lesions such as lentigo maligna, other approaches (for example, a topical medication or radiation) are sometimes used. When melanoma has spread to lymph nodes or beyond, modern immunotherapy (drugs that help the immune system attack the cancer) and, for tumors with specific gene changes, targeted therapy have substantially improved outcomes. Details are on the treatment of melanoma page.