Malignant skin lesions/tumors commonly called skin cancers are the most common cancers in the population. This is not surprising because skin happens to be the largest organ in the body and it is in contact directly or indirectly with a lot of carcinogens like ultra-violet radiation, a chemical carcinogen in the environment.

There are three major types of skin cancers: basal cell carcinomas (BCC), squamous cell carcinoma (SCC), and melanoma. The first two skin cancers are grouped together as non-melanoma skin cancers. Other unusual types of skin cancer include Merkel cell tumors and dermatofibrosarcoma protuberance.

The vast majority of skin cancers are basal cell carcinomas and squamous cell carcinomas. While malignant, these are unlikely to spread to other parts of the body. They may be locally disfiguring if not treated early. Left untreated SCC is more likely to spread to other areas than BCC.

A small but significant number of skin cancers are malignant melanomas. Malignant melanoma is a highly aggressive cancer that tends to spread to other parts of the body. These cancers may be fatal if not treated early.

Like many cancers, skin cancers start as precancerous lesions. These precancerous lesions are changes in skin that are not cancer but could become cancer over time. Medical professionals often refer to these changes as dysplasia. Some specific dysplastic changes that occur in skin are as follows:

Actinic keratosis
is an area of red or brown, scaly, rough skin, which can develop into squamous cell carcinoma or basal cell carcinoma. They are found mainly in the sun-exposed areas.

A nevus is a mole, and abnormal moles are called dysplastic nevi. These can potentially develop into melanoma over time.

Early recognition of malignant or precancerous lesions is important because complete excision will cure almost all cases of skin cancer if performed in the early stages.