Types of skin cancer include basal and squamous cell carcinoma, melanoma and Merkel cell carcinoma.
Basal and squamous cell carcinomas, the most common types of skin cancer, start on the top layer of the skin. Squamous cells are flat cells in the outer part of the epidermis, while basal cells are in the lower part of the epidermis. Both types commonly appear on sun-exposed parts of the body, and can usually be removed completely; however, they can grow into deeper layers of skin and spread to other parts of the body.
Melanoma develops from melanocytes, which make the brown pigment that gives skin its tan or brown color. Melanoma is less common; however, it is more likely to grow and spread if untreated.
Merkel cell carcinoma, also called neuroendocrine carcinoma of the skin, is also less common; however, it can be the most dangerous because it is more likely to spread to other parts of the body and can be very hard to treat if it has spread.