Skin Cancer: Symptoms, Causes, Prevention, and Treatment
Also known as: Melanoma, Basal cell carcinoma, Squamous cell carcinoma, Nonmelanoma skin cancer
Overview
Skin cancer is the most common cancer in the United States. More than 5 million cases of basal and squamous cell skin cancer are diagnosed each year, and about 112,000 new invasive melanomas are diagnosed annually, according to the American Academy of Dermatology (AAD) and the American Cancer Society (ACS). Skin cancer refers to abnormal, uncontrolled growth of skin cells. The main types are basal cell carcinoma and squamous cell carcinoma (the most common and generally less aggressive), and melanoma, the most serious form because of its high potential to spread. Rates have risen steadily for decades, and while skin cancer affects all age groups, it is more common after age 50.
Causes and risk factors
The main risk factor is exposure to ultraviolet (UV) radiation, whether from the sun or artificial sources such as tanning beds. People with fair skin tones (light skin, eyes, and hair) are especially vulnerable. Other factors include a personal or family history of skin cancer, having many moles (nevi), a weakened immune system (immunosuppression or immunosuppressive treatments), occupational exposure to carcinogens such as arsenic and tar, and repeated sunburns during childhood.
Symptoms
Signs vary by cancer type. For melanoma, the ABCDE rule is essential: Asymmetry of a mole, irregular Borders, uneven Color, a Diameter larger than 6 mm (about the size of a pencil eraser), and a mole that is Evolving in size, shape, or color. Basal cell carcinomas often appear as a small, pearly or pink bump that does not heal. Squamous cell carcinomas show up as a thick, scaly patch or an ulceration. Any change in a mole’s appearance or any sore that will not heal should prompt medical attention.
Diagnosis
Diagnosis is made by a dermatologist through a clinical exam with dermoscopy (a specialized magnifying tool used to examine skin structures). If skin cancer is suspected, a skin biopsy is performed for pathology analysis. For melanoma, additional imaging or a sentinel lymph node biopsy may be done to check for spread and determine the stage.
Treatments
Treatment depends on the type, stage, and location of the tumor, and is discussed by a multidisciplinary care team:
- Surgery: removal of the lesion with a safety margin, the standard treatment for most skin cancers
- Immunotherapy and targeted therapy: used for advanced or metastatic melanoma (anti-PD-1 drugs, BRAF/MEK inhibitors)
- Radiation therapy: used as a complement or when surgery is not possible
- Topical chemotherapy (cream) or photodynamic therapy for certain superficial carcinomas
- Close follow-up after treatment to catch any recurrence early
Prevention
Prevention relies mainly on sun protection. Apply a broad-spectrum sunscreen with an SPF of 30 or higher, and reapply about every two hours, or after swimming or sweating. Wear protective clothing, a wide-brimmed hat, and sunglasses. Seek shade when the sun is strongest, between 10 a.m. and 2 p.m., and avoid tanning beds altogether. A monthly skin self-exam helps catch suspicious lesions early. People at higher risk (family history, fair skin, many moles) should ask their doctor how often to have their skin checked.
When should you see a doctor?
See a doctor promptly if you notice a mole that is changing shape, color, or size, a sore that bleeds or has not healed after several weeks, or a lesion that bleeds spontaneously or itches. Any unusual skin change deserves prompt medical evaluation, especially after repeated intense sun exposure.
Sources
- American Academy of Dermatology: skin cancer statistics, skin cancer as the most common cancer in the US and about 112,000 new invasive melanomas estimated in 2026
- American Academy of Dermatology: how to prevent skin cancer, broad-spectrum SPF 30 or higher reapplied every two hours, seeking shade when the sun is strongest between 10 a.m. and 2 p.m., protective clothing, avoiding tanning beds, and skin self-exams
- American Cancer Society: melanoma key statistics, about 112,000 new melanomas estimated in the US in 2026
- American Cancer Society: basal and squamous cell skin cancer key statistics, more than 5 million basal and squamous cell skin cancers diagnosed each year and skin cancer as the most common cancer
- American Cancer Society: melanoma signs and symptoms, the ABCDE rule and the 6 mm (pencil-eraser) diameter guide
- American Cancer Society: basal and squamous cell skin cancer signs and symptoms, pearly bumps and scaly patches and a sore that bleeds or does not heal after several weeks
- American Cancer Society: melanoma risk factors, fair skin, many moles, family and personal history, weakened immune system, and sunburns in childhood
- American Cancer Society: basal and squamous cell skin cancer risk factors, UV exposure, arsenic, and coal tar as risk factors
- American Cancer Society: how melanoma is diagnosed, dermatologist exam, dermoscopy, skin biopsy, and sentinel lymph node biopsy
- American Cancer Society: treating melanoma, surgery, immunotherapy, targeted therapy, and radiation
- American Cancer Society: treating basal and squamous cell skin cancer, surgery and non-surgical local treatments for superficial carcinomas
- American Cancer Society: skin exams, a monthly skin self-exam and asking your doctor how often to have your skin checked
- MedlinePlus: skin cancer, skin cancer more common after age 50 and melanoma as the more dangerous but less common type