Each type of skin cancer has particular symptoms. Changes in the size, shape or color of a mole may be cause for concern. Sores that do not heal are another danger sign and should be examined immediately by a dermatologist. Basal skins cancers most frequently occur on parts of the body that are constantly exposed to the sun and may present as existing moles and freckles that get larger, or look like pimples or sores. Squamous cell carcinoma, the second most common type of skin cancer, often occurs in similar areas to basal skin cancers and is prevalent in fair-skinned people who have spent a lot of time in the sun. 95% of cases of squamous cell carcinoma can be cured if they are diagnosed early, so it is important to know the warning signs: crusted skin, scaly skin, growths that resemble tumors or ulcers that do not heal. 

Melanoma is the most dangerous form of skin cancer; however, the term melanoma can be misleading as all melanomas are not cancerous. A melanoma is simply a dark spot or mole formed after years of sun exposure, and can be benign or malignant. A benign mole is called a nevus, as is a birthmark. Malignancy can be determined by a biopsy. Malignant melanomas can occur literally anywhere on the body, which is why it is so important for people to regular check their own bodies for moles and see a dermatologist for regular mole checks. Asymmetric moles, moles with uneven borders, multi-colored moles and moles the size of a pencil eraser or larger may potentially be malignant. However, large moles may also be benign, but any moles with the above symptomatology need to be examined by a dermatologist.

Basal cell carcinoma, squamous cell carcinoma and malignant melanoma are the most common types of skin cancer. Merkel cell carcinoma, a rare and aggressive skin cancer, occurs most often in older people and presents as a flesh-colored or bluish red nodule, usually in the area of the face or head. As this is a fast-growing cancer, it tend to spread to other parts of the body. This is called metastasis. Cancers that have metastasized are much more difficult to treat.

It is best to take precautions to guard against blistering sunburns and long-term sun exposure. If suspicious growths are found on the skin, seeking a diagnose and treatment immediately greatly increases the chance of a cure or extending survival.