Skin cancer is characterized by uncontrolled, abnormal cell growth on the skin, and various types arise from different skin cells. The 3 main types are basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma; BCC and SCC are known as nonmelanoma skin cancer (NMSC).

The main signs of skin cancer include changes in skin appearance, which vary by type: basal cell carcinoma (BCC) appears as shiny, translucent bumps; squamous cell carcinoma (SCC) appears as pink to red, scaly bumps; and melanoma typically manifests as asymmetrical brown to black lesions with irregular borders. These cancers commonly occur on sun-exposed areas of the skin, such as the face and neck.

Skin cancer is diagnosed through a visual examination by a medical professional, followed by a biopsy if cancer is suspected. In cases of melanoma, additional clinical examinations and tests may be conducted to check for metastasis.

The main treatment for skin cancer is surgical removal of the tumor, which may be supplemented by additional therapies such as radiation, chemotherapy, immunotherapy, or photodynamic therapy, depending on the case specifics. Surgery is often effective on its own, but some situations may necessitate further intervention.

Several studies indicate that niacinamide supplementation may lower the risk of nonmelanoma skin cancer (NMSC) in people with a history of skin issues, whereas oral retinol has been shown to reduce the risk of squamous cell carcinoma (SCC), but not basal cell carcinoma (BCC). In contrast, beta-carotene showed no effect on NMSC risk, and selenium supplementation was found to increase SCC risk in certain individuals.

Diet can influence skin cancer risk; higher coffee consumption is associated with a lower risk of basal cell carcinoma (BCC) and melanoma, whereas increased citrus fruit intake may raise melanoma risk due to psoralens. Additionally, higher alcohol consumption is associated with an increased risk of BCC, squamous cell carcinoma (SCC), and melanoma, whereas greater retinol intake may lower melanoma risk.

Acitretin, a synthetic retinoid typically used for psoriasis, can be administered orally to lower the risk of skin cancer, particularly in individuals who are at high risk, such as immunocompromised transplant recipients. However, its use is limited due to the potential for severe side effects.

Skin cancer is primarily caused by exposure to ultraviolet (UV) light, particularly from sunlight, and increased risk is associated with cumulative sun exposure and frequency of sunburns. Other contributing factors include skin color and the use of tanning beds, photosensitizing medications, and immunosuppressive drugs, which can elevate the risk of developing skin cancer.