Prevention of skin cancer is of primary concern during summer months in most areas of the United States and year-round in latitudes with intensive UV exposure. The single most important primary preventative measure against skin cancer is avoidance of sun exposure. Both UVA and UVB rays can cause damage to cellular DNA leading to development of skin cancer.  Patients must be educated on appropriate use and application of sunscreen and sun-protective clothing.

Skin cancer is classified as melanoma versus non-melanoma. Worldwide, there are between 2-3 million newly diagnosed cases of non-melanoma skin cancer and over 200,000 newly diagnosed cases of melanoma each year. Basal cell carcinomas are the most common type of cancer diagnosed in the United States each year and account for 70-80% of non-melanoma skin cancers.  The primary cause of basal cell carcinoma is UV radiation from the sun. The lesions of basal cell carcinoma may have a varied appearance, ranging from very subtle to very aggressive, often leading to a delay in diagnosis.  Diagnosis is typically made by biopsy or at the time of excision. Basal cell carcinoma has <0.1% chance of metastasis.

Squamous cell carcinoma is a more aggressive type of non-melanoma skin cancer. Squamous cell carcinoma, like basal cell carcinoma, is also predominately caused from sun exposure. The appearance of squamous cell carcinoma can vary, ranging from an erythematous, ulcerated lesion to a more superficial area of erosion. Diagnosis is most often made by biopsy or at the time of excision if the lesion is small. Squamous cell carcinoma is much more likely to metastasize as compared with basal cell carcinoma, with cutaneous squamous cell carcinoma cases exhibiting metastasis in up to 5.2% of cases.

Melanoma is a very aggressive type of skin cancer, and accounts for the majority of skin cancer-related deaths. The risk for developing melanoma is associated with factors such as the presence of multiple nevi, genetic risk factors (including family history), and sun exposure.  As with prevention of other types of skin cancer, protection from sun exposure is paramount. Patients should also be taught to report any changes associated with the shape or appearance of nevi, which may be an indication for removal. Diagnosis is most often made by biopsy or at the time of excision if the lesion is small.  The survival of patients with melanoma depends upon stage at diagnosis.  More than 80% of patients that are diagnosed with melanoma have disease confined to the skin at the time of presentation with only about 4% having advanced metastasis at initial diagnosis.

Read more about skin cancer and skin cancer prevention:

Harrison's Principles of Internal Medicine, 20e: Chapter 72: Cancer of the Skin

Centers for Disease Control and Prevention: Skin Cancer