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What is Melanoma?
The skin is made up of three layers: the outermost, called the epidermis, the middle layer called the dermis, and the innermost layer, called the hypodermis, which is composed of fat (Figure).1 The epidermis includes three cell types: squamous cells, basal cells, and melanocytes. The melanocytes are found in the inner layer of the epidermis and are responsible for skin color.1
Melanoma forms when melanocytes start to grown and spread more quickly than normal cells.1
Broadly, the four main types of melanomas are:
- Superficial spreading melanoma
- Lentigo maligna melanoma
- Nodular melanoma
- Acral lentiginous melanoma
Superficial spreading melanoma is the most common type, followed by nodular melanoma.2 Lentigo maligna is a slow growing melanoma and is commonly seen in areas exposed often to the sun.2,3 Acral lentiginous melanomas typically develop in darker skinned people, appear on the palms, soles, and under the nail bed.2
After melanoma is diagnosed, your doctor may order testing to see if the cancer has changes (mutations) in certain genes (Table 1).4 Some gene changes help your doctor decide what treatment to use.
Stages of Melanoma
Doctors “stage” the cancer to find out how much cancer there is and if it has spread anywhere.4 The TNM system is used to stage cancer.
- T stands for tumor. It tells how thick the tumor is (Breslow measurement) and if there is an ulceration. The smaller the T stage, the smaller the cancer.
- N stands for lymph nodes. It tells if the cancer has spread to any lymph nodes near the main tumor.
- M stands for metastasis. It tells if the cancer has spread to lymph nodes far from the main tumor and/or to other organs in the body.5
A sentinel lymph node biopsy can also be used for staging of melanomas, and further information can be found in the Symptoms and Diagnosis section.5
Statistics
Melanoma is the fifth most common cancer among men and women in the United States (Table 3).6 In 2025, the United States is expected to have about 60,550 men and 44,410 women diagnosed with melanoma.11 The average age of diagnosis is 65 years.
Risk Factors
Melanoma, when detected early, can often be cured with surgery. Metastatic or advanced melanoma is one of the most serious forms of skin cancer, and early detection is key to a good prognosis.6
Anyone can get skin cancer, but there are certain things that increase your risk of getting it, such as:
- Light or fair skin color
- Skin that burns, freckles, or turns red easily
- Blue or green eyes
- Blond or red hair
- Moles
- A history of sunburns or tanning
- A family member with skin cancer
- Prior skin cancer
- Older age7
References
- National Cancer Institute. Skin cancer Prevention (PDQ)-Patient Version. https://www.cancer.gov/types/skin/patient/skin-prevention-pdq
- National Cancer Institute. SEER Training Modules. Types of Melanoma. https://training.seer.cancer.gov/melanoma/intro/types.html
- StatPearls. Lentigo Maligna Melanoma. October 31, 2022. https://www.ncbi.nlm.nih.gov/books/NBK482163/
- American Cancer Society. Tests for Melanoma Skin Cancer. Updated October 27, 2023. https://www.cancer.org/cancer/types/melanoma-skin-cancer/detection-diagnosis-staging/how-diagnosed.html
- American Cancer Society. Melanoma Skin Cancer Stages. Updated October 27, 2023. https://www.cancer.org/cancer/types/melanoma-skin-cancer/detection-diagnosis-staging/melanoma-skin-cancer-stages.html
- American Cancer Society. Cancer Facts & Figures, 2025. https://www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/2025-cancer-facts-figures.html
- Centers for Disease Control and Prevention. Skin Cancer Risk Factors. https://www.cdc.gov/skin-cancer/risk-factors/index.html
All URLs accessed May 6, 2025
