Skin cancer is a type of cancer that occurs when there is an abnormal growth of skin cells, usually triggered by damage to the DNA within the skin cells. It is primarily caused by exposure to ultraviolet (UV) radiation from the sun or artificial sources like tanning beds. Skin cancer is the most common type of cancer worldwide, and its incidence continues to rise.

Basal Cell Carcinoma (BCC): BCC is the most common type of skin cancer, accounting for about 80% of cases. It typically develops in skin areas frequently exposed to the sun, such as the face, scalp, neck, and hands. BCC usually appears as a small, raised, translucent or pearly bump that may develop into an open sore, a red patch, or a shiny growth. BCC rarely spreads to other parts of the body but can invade nearby tissues if left untreated. Although UV rays are the main culprit, exposure to other agents, such as radiation and arsenic, can also lead to this type of cancer. Wounds on the skin due to open sores, tattoos, and burns may also be predisposing factors. Basal cell carcinomas start in the stratum basale and usually spread along this boundary. At some point, they begin to grow toward the surface and become an uneven patch, bump, growth, or scar on the skin's surface. Like most cancers, basal cell carcinomas respond best to treatment when caught early. Treatment options typically involve surgical procedures. If surgery is not an option, topical ointments are prescribed.

Squamous Cell Carcinoma (SCC): SCC is the second most common type of skin cancer. SCC affects the keratinocytes of the stratum spinosum and presents as lesions commonly found on the scalp, ears, and hands. It is the second most common skin cancer. This is more aggressive than basal cell carcinoma. If not removed, these carcinomas can metastasize. Surgery and radiation are used to cure squamous cell carcinoma.

Melanoma: Although less common than BCC and SCC, melanoma is the most aggressive and potentially deadly form of skin cancer. Melanoma is a cancer characterized by the uncontrolled growth of melanocytes, the pigment-producing cells in the epidermis. Typically, melanoma develops from a mole. It is the most fatal of all skin cancers, as it is highly metastatic and can be difficult to detect before it has spread to other organs. Melanomas usually appear as asymmetrical brown and black patches with uneven borders and a raised surface. Treatment typically involves surgical excision and immunotherapy.

There is an ABCDE mnemonic to help diagnose early-stage melanoma.

• Asymmetry – the two sides are not symmetrical.
• Borders – the edges are irregular in shape.
• Color – the color is varied shades of brown or black.
• Diameter – it is larger than 6 mm (0.24 in).
• Evolving – its shape has changed.

If diagnosed with skin cancer, treatment options depend on the type, size, location, and stage of the cancer. Common treatments include surgical excision, Mohs surgery, radiation therapy, topical medications, cryotherapy, and targeted therapy or immunotherapy for advanced cases.

This text is adapted from Openstax, Anatomy and Physiology 2e, Section 5.4: diseases disorders and injuries of the integumentary system