What Is Melanoma? Symptoms, Causes, and Risk Factors

Melanoma is a cancer of the pigment-producing cells in the skin called melanocytes. These cells normally exist throughout the skin, producing the melanin that gives skin its color and provides modest natural protection against ultraviolet damage. When melanocytes acquire genetic changes that disrupt the normal regulation of cell growth, the affected cells can grow into a tumor that can invade deeper tissues and potentially spread to other parts of the body.

The clinical importance of melanoma reflects its specific biology. While melanoma accounts for a smaller proportion of all skin cancers than basal cell carcinoma or squamous cell carcinoma, it is responsible for the majority of skin cancer deaths. The reason is its capacity to metastasize. Once melanoma cells acquire the ability to invade and spread, they can travel through lymphatic channels and blood vessels to distant sites, where they can form new tumors that are far more difficult to treat than the original lesion.

The encouraging reality is that melanoma is highly treatable when identified at early stages. Most melanomas can be detected through visual examination of the skin, often by patients themselves. The features that distinguish concerning lesions from benign ones can be learned. Modern dermatologic care, including dermoscopy and various other tools, supports accurate diagnosis. Treatment outcomes for early-stage melanoma are excellent, with the great majority of patients cured by surgical removal alone. Even for advanced disease, modern immunotherapy and targeted therapy have transformed what was once a uniformly devastating diagnosis into a condition with meaningful treatment options.

This article provides a foundational overview of melanoma, including what it is, what causes it, who is at risk, what symptoms suggest its presence, and how it is generally diagnosed and treated.

For more detail on melanoma broadly, see Melanoma: Early Detection Saves Lives — The "Ugly Duckling" Sign Explained.

What Melanoma Actually Is at the Cellular Level

Melanoma develops from melanocytes, the cells in the skin that produce melanin. Melanocytes normally exist in the basal layer of the epidermis, where they produce pigment that protects deeper skin layers from ultraviolet damage. They also exist in other locations including the eyes, the inner surfaces of the nose and mouth, and various other sites where pigmented tissues are found.

The transformation from normal melanocyte to melanoma cell involves accumulation of genetic changes. The most common changes affect specific genes that regulate cell growth and division. Approximately half of melanomas carry mutations in the BRAF gene, with smaller proportions carrying mutations in NRAS, KIT, and various other genes. These genetic changes disrupt normal regulation, allowing affected cells to continue growing rather than dying off as they normally would.

Once these changes have occurred, melanoma cells can grow into a visible tumor on the skin or other affected tissues. The tumor initially grows in place, sometimes for years, before some cells acquire additional changes that allow invasion of deeper tissues and ultimately the capacity to spread.

How Melanoma Develops

Several specific patterns describe how melanoma develops.

From Existing Moles

Some melanomas develop from existing moles. A mole that has been present for years can undergo transformation, with cells acquiring the genetic changes that produce malignancy. The transformation is typically gradual, with subtle changes preceding more obvious ones. The features that signal this transformation include changes in the size, shape, color, or other characteristics of the mole.

The proportion of melanomas that arise from existing moles is approximately 25 to 33 percent in most studies. This means that the majority of melanomas arise from previously normal-appearing skin rather than from existing moles.

On Previously Normal Skin

The majority of melanomas arise on previously normal skin, with no preceding visible lesion. The melanoma develops from melanocytes in the affected area that acquire genetic changes and grow into a tumor. The result is a new lesion that may resemble a mole but did not exist as a recognizable lesion before.

This pattern has implications for surveillance. Looking only at existing moles for changes misses the substantial proportion of melanomas that arise as new lesions. Comprehensive skin examination requires attention to both existing lesions and any new lesions that appear.

Subtype Patterns

Different subtypes of melanoma have somewhat different developmental patterns.

Superficial spreading melanoma, the most common subtype, typically grows horizontally across the skin for a period before invading deeper tissues. This horizontal growth phase provides time for detection.

Nodular melanoma grows more rapidly downward into the skin, sometimes without a substantial horizontal phase. This pattern can produce more aggressive lesions that warrant prompt attention.

Lentigo maligna melanoma typically develops in older adults on chronically sun-damaged skin. The lesions often grow slowly over years before becoming invasive.

Acral lentiginous melanoma develops on palms, soles, and under nails. This subtype is more common in people with darker skin and is often diagnosed at later stages.

What Causes Melanoma

The causes of melanoma include both environmental and inherited factors, with the combination determining individual risk.

Ultraviolet Exposure

Ultraviolet exposure from the sun and tanning beds is the most important environmental cause of melanoma. The relationship is complex, with intermittent intense exposure producing burns being more strongly associated with melanoma risk than chronic continuous exposure.

The biological mechanism involves DNA damage from ultraviolet radiation. Most damage is repaired by cellular machinery, but some persists. The accumulated damage over years and decades produces the genetic changes that drive cancer development.

Childhood and adolescent exposure carries particular weight. Multiple severe sunburns during these life stages substantially elevate adult melanoma risk. The skin is more vulnerable during developmental periods, and damage during these periods produces lasting susceptibility.

For more on this, see Sun Exposure and Skin Cancer: What You Need to Know.

Genetic Susceptibility

Inherited genetic factors influence melanoma risk through multiple pathways.

High-penetrance susceptibility genes, including CDKN2A, CDK4, BAP1, and others, substantially elevate lifetime risk in carriers. These mutations are uncommon but produce risk increases of 50 percent or higher in the strongest cases.

Moderate-penetrance genes, including MC1R, contribute to risk in many individuals through more modest effects.

Inherited skin characteristics including fair skin, light hair, light eye color, and tendency to freckle and burn affect how the skin responds to ultraviolet damage and contribute to melanoma risk independently of specific susceptibility mutations.

Other Risk Factors

Several other factors contribute to melanoma risk including immunosuppression from organ transplantation, HIV infection, or autoimmune treatment, history of multiple severe sunburns, large numbers of moles, presence of atypical moles, prior history of melanoma or other skin cancers, and family history of melanoma.

For more comprehensive information on risk factors, see Who Is at Risk for Melanoma? Understanding the Key Risk Factors.

Symptoms of Melanoma

Melanoma typically presents as a visible change in the skin. Several specific patterns warrant attention.

Changes in Existing Moles

When melanoma develops from an existing mole, the changes follow specific patterns captured in the ABCDE rule.

Asymmetry: one half of the lesion does not match the other.

Border irregularity: edges become ragged, scalloped, or notched.

Color variation: multiple colors appear within the lesion, including combinations of brown, black, tan, red, white, or blue.

Diameter greater than 6 millimeters, though smaller melanomas can occur.

Evolution: changes over time in size, shape, color, or other features.

New Lesions Appearing

A new lesion appearing in adulthood, particularly after age 30 or 40, warrants evaluation. While new benign moles can occasionally appear in adulthood, the development of new lesions raises somewhat higher concern than new lesions appearing in childhood.

The Ugly Duckling Sign

A lesion that looks distinctly different from other moles on the same person, the "ugly duckling," warrants attention. The principle reflects the biological pattern that benign moles on any individual generally look similar to each other, while concerning lesions often stand out as different.

Specific Symptoms in Lesions

Several specific symptoms in moles warrant attention. Persistent itching at the lesion site. Bleeding, even minor or occasional bleeding. Tenderness or pain. Surface changes including scaling, crusting, or ulceration. Loss of pigment in areas of the lesion (regression).

Symptoms of Advanced Disease

When melanoma has spread beyond the original site, additional symptoms may develop based on the location of metastases. Lung metastases can produce cough or shortness of breath. Brain metastases can produce headaches, neurological symptoms, or seizures. Liver metastases can produce abdominal symptoms. Bone metastases can produce pain. Lymph node involvement can produce visible lumps in the affected nodes.

For more on warning signs, see Early Signs of Melanoma: The ABCDE Rule Explained.

Where Melanoma Develops

Melanoma can develop anywhere on the body where melanocytes exist, with some locations being more common than others.

In men, the most common location is the trunk, particularly the back. The shoulders, neck, and other areas are also common.

In women, the most common location is the legs, with the trunk and arms also frequently affected.

In people of any sex, melanoma can develop in less common locations including the scalp, palms, soles, under nails, the genitals, and various other sites. These locations can be missed during self-examination because they are not always carefully inspected.

Melanoma can also develop in non-cutaneous sites including the eye (uveal melanoma), the inner surfaces of the mouth and nose (mucosal melanoma), and various other sites where melanocytes exist.

Acral Locations

Melanoma on palms, soles, and under nails (acral locations) deserves specific attention. Acral lentiginous melanoma is a specific subtype that develops in these locations and is the most common type of melanoma in people with darker skin.

Pigmented streaks under nails, particularly when wider than 3 millimeters, irregular, affecting only one nail, or extending into surrounding nail tissue, warrant evaluation.

Less Common Sites

Less common sites for cutaneous melanoma include the scalp, the buttocks, the genital area, and various others. Self-examination of these areas can be challenging, and professional examination supports systematic evaluation.

For non-cutaneous melanoma, specific symptoms vary by site. Uveal melanoma may produce visual changes or be detected on routine eye examination. Mucosal melanoma may produce site-specific symptoms.

How Melanoma Is Diagnosed

The diagnosis of melanoma involves a sequence of steps that progresses from initial visual assessment to definitive pathological confirmation.

Clinical Examination

The diagnostic process typically begins with clinical examination by a dermatologist or other qualified clinician. The examination evaluates the skin systematically, looking for any concerning lesions based on ABCDE features and the ugly duckling sign.

Dermoscopy

For lesions warranting closer evaluation, dermoscopy provides additional information. The technique uses a handheld device that magnifies the skin and reveals patterns below the surface that are invisible to the naked eye. Dermoscopy substantially improves diagnostic accuracy compared to visual examination alone.

For more on dermoscopy, see Dermoscopy: What Dermatologists Look For When Examining Skin Lesions.

Biopsy

For lesions where clinical and dermoscopic examination suggests possible melanoma, biopsy provides definitive diagnosis. Excisional biopsy with complete removal of the lesion is the preferred technique for suspected melanoma, allowing complete pathological evaluation including measurement of depth.

The biopsy specimen is examined by a pathologist, who provides detailed information including the type of melanoma, the depth of invasion (Breslow thickness), the presence or absence of ulceration, the mitotic rate, and various other features. These features inform staging and treatment decisions.

Staging Evaluation

Once melanoma is diagnosed, staging evaluation determines the extent of disease. The TNM staging system classifies melanoma based on the primary tumor (T), the involvement of regional lymph nodes (N), and the presence of distant metastases (M). The combined staging from Stage 0 through Stage 4 provides the framework for treatment decisions.

For melanomas with thickness greater than approximately 0.8 millimeters, sentinel lymph node biopsy is often recommended to assess whether cancer has spread to regional lymph nodes. For more advanced disease, imaging studies may evaluate for distant metastases.

How Melanoma Is Treated

Treatment depends on the stage of disease and various individual factors.

Surgery

Surgical removal of the primary melanoma is the foundation of treatment for most patients. Wide local excision removes the melanoma along with appropriate margins of surrounding skin. For most early-stage melanomas, surgical removal alone provides definitive treatment.

For melanomas with thickness greater than approximately 0.8 millimeters, sentinel lymph node biopsy is often performed at the same time as wide local excision. The procedure assesses whether cancer has spread to regional lymph nodes.

Adjuvant Therapy

For patients with Stage 3 melanoma after surgical removal, adjuvant therapy with immunotherapy or targeted therapy substantially reduces recurrence rates. The use of adjuvant therapy has expanded to include selected patients with Stage 2 melanoma at higher risk of recurrence.

Systemic Therapy for Advanced Disease

For metastatic melanoma, systemic therapy provides effective treatment. Modern options include immunotherapy with PD-1 inhibitors (pembrolizumab, nivolumab), CTLA-4 inhibitors (ipilimumab), and combinations of these agents. Targeted therapy with BRAF and MEK inhibitor combinations is effective for melanomas with BRAF mutations.

The introduction of immunotherapy and targeted therapy has transformed outcomes for advanced melanoma, with substantially improved response rates and durability compared to older treatments.

Radiation Therapy

Radiation therapy has specific roles in melanoma treatment, particularly for brain metastases through stereotactic radiosurgery and for certain other specific situations.

Outcomes by Stage

The prognosis for melanoma varies dramatically by stage at diagnosis.

For Stage 0 melanoma (melanoma in situ), the five-year survival rate approaches 100 percent. Surgical removal is essentially curative.

For Stage 1 melanoma, the five-year survival rate is approximately 95 to 99 percent. Most patients are cured by surgical treatment alone.

For Stage 2 melanoma, the five-year survival rate ranges from approximately 60 to 95 percent depending on the specific substage.

For Stage 3 melanoma, with regional lymph node involvement, the five-year survival rate has historically ranged from approximately 20 to 85 percent depending on substage. Modern adjuvant therapy has substantially improved outcomes.

For Stage 4 melanoma, with distant metastases, the historic five-year survival rate of 15 to 20 percent has been transformed by modern immunotherapy. Five-year survival rates in clinical trials of combination immunotherapy have reached approximately 50 percent or higher in selected populations.

For more on stages and outcomes, see Melanoma Survival Rates by Stage: What the Numbers Really Mean.

The Importance of Early Detection

The dramatic difference in outcomes by stage emphasizes the importance of early detection. The single most powerful determinant of melanoma outcomes is when the cancer is identified.

A melanoma identified at Stage 1 has cure probability approaching 99 percent. The same melanoma, if allowed to progress to Stage 4, would have substantially different outcomes despite modern treatment. The investment in detection and surveillance produces benefits measured in lives saved.

For the general population, several practical approaches support early detection.

Regular self-examination of the skin, performed approximately once a month, supports awareness of any new or changing lesions. The principles of self-examination apply to lesions of any size, with attention to the ABCDE features and the ugly duckling sign.

Periodic professional skin examinations provide more thorough evaluation. The frequency depends on individual risk factors, with annual examinations typical for moderate-risk individuals.

Awareness of warning signs supports recognition of concerning lesions when they develop.

For higher-risk individuals, more intensive surveillance including dermoscopy, total body photography, and more frequent professional examinations supports early detection.

Prevention

Several specific approaches support melanoma prevention.

Sun Protection

Sun protection is the most important preventable factor for melanoma. Effective sun protection includes broad-spectrum sunscreen with SPF 30 or higher, protective clothing, wide-brimmed hats, avoidance of peak sun exposure during midday hours, and complete avoidance of tanning beds.

The cumulative effect of consistent sun protection over a lifetime substantially reduces ultraviolet damage that contributes to melanoma development.

Avoidance of Tanning Beds

Tanning beds substantially elevate melanoma risk and have no health benefit. Complete avoidance is recommended for all individuals.

Surveillance

Regular skin examinations, both self-examination and professional examination, support detection of any developing melanomas at early stages where treatment is most effective.

Awareness

Awareness of warning signs, the ABCDE features, and the ugly duckling sign supports recognition of concerning lesions when they develop.

For more on prevention, see Sun Exposure and Skin Cancer: What You Need to Know.

Special Populations

Several specific populations warrant attention regarding melanoma.

People With Darker Skin

Melanoma occurs less commonly in people with darker skin, but the condition is often diagnosed at later stages because of less recognition of risk and less common surveillance. Acral lentiginous melanoma on palms, soles, and under nails accounts for a higher proportion of cases in this population.

For people with darker skin, attention to acral locations and any new or changing lesions supports detection.

Children and Adolescents

Melanoma is uncommon in children and adolescents, but it can occur. Concerning features in children include rapidly growing lesions, lesions with significant ABCDE features, and lesions that bleed or ulcerate. Pediatric dermatology consultation is appropriate for concerning lesions in this age group.

Pregnant Women

Hormonal changes during pregnancy can produce changes in existing moles. Most of these changes are benign, but evaluation remains appropriate for any mole showing distinctly concerning features. Melanoma during pregnancy can be diagnosed and treated, with management individualized based on the specific clinical situation.

Older Adults

Melanoma incidence increases with age. Older adults benefit from continued surveillance regardless of any history of skin cancer. Lentigo maligna melanoma, which is more common in older adults, often grows slowly over years and can be challenging to recognize without dermatologic examination.

Living With and After Melanoma

For patients diagnosed with melanoma, several considerations affect long-term care.

Surveillance for recurrence and new primary melanomas continues for many years after initial treatment. Risk of recurrence is highest in the first few years but declines progressively over time.

Risk of new primary melanomas is elevated in patients who have had one melanoma. The lifetime risk of a second primary melanoma is approximately 5 to 10 percent, substantially higher than the general population risk. Ongoing skin surveillance throughout life is essential.

Sun protection becomes a lifelong priority. Avoiding ultraviolet exposure through clothing, broad-spectrum sunscreen, and avoidance of tanning supports both prevention of new skin cancers and overall skin health.

Psychological adjustment to the experience of having had melanoma is part of the long-term picture. Support is available through cancer-specific counseling, support groups, and integration of mental health care with ongoing surveillance.

For more on cure and recovery, see Can Melanoma Be Cured? Understanding the Reality of Treatment and Recovery.

When to See a Specialist

Several situations warrant dermatologic consultation regarding melanoma.

Any new mole appearing in adulthood, particularly in patients over 30, warrants evaluation.

Existing moles showing changes in size, shape, color, or other features warrant evaluation.

Lesions showing any of the ABCDE features warrant evaluation.

Lesions causing symptoms including itching, bleeding, or persistent ulceration warrant evaluation.

Patients with significant risk factors for melanoma benefit from regular dermatologic surveillance.

For patients diagnosed with melanoma, multidisciplinary care including dermatology, surgical oncology, and medical oncology when needed provides comprehensive care.

Conclusion

Melanoma is a cancer of pigment-producing cells in the skin. While it accounts for a smaller proportion of skin cancers than other types, it is responsible for the majority of skin cancer deaths because of its capacity to spread to distant sites.

The encouraging reality is that melanoma is highly treatable when identified at early stages. Most melanomas can be detected through visual examination, often by patients themselves. The features that distinguish concerning lesions from benign ones can be learned through frameworks including the ABCDE rule and the ugly duckling sign. Modern dermatologic care, including dermoscopy and biopsy, supports accurate diagnosis. Treatment outcomes for early-stage melanoma are excellent, with the great majority of patients cured by surgical removal alone.

For advanced disease, modern immunotherapy and targeted therapy have transformed what was once a uniformly devastating diagnosis into a condition with meaningful treatment options. The trajectory of melanoma care continues to improve, with ongoing research expanding the options available.

For most individuals, the practical message is that awareness, prevention, and surveillance support the best possible outcomes. Sun protection through sunscreen, protective clothing, and avoidance of tanning beds reduces ultraviolet damage. Self-examination and professional surveillance support detection of any concerning lesions at stages where treatment is most effective. The combination of these approaches produces the best chance of preventing melanoma when possible and detecting any developing cancer at the earliest stage.

The investment in understanding melanoma, recognizing warning signs, and engaging with appropriate prevention and surveillance produces meaningful benefits with relatively modest effort. For most people, the result is reassurance that they will not develop melanoma. For the substantial minority who do, early detection through awareness and surveillance produces excellent outcomes for the great majority.

Medical Disclaimer

This content is for informational purposes only and does not constitute medical advice. Individuals should consult a qualified healthcare provider for diagnosis and treatment.