Skin cancer is the most common of all cancers.It is the most common form of human cancer. It is estimated that over 1 million new cases occur annually. The annual rates of all forms of skin cancer are increasing each year, representing a growing public concern. It has also been estimated that nearly half of all Americans who live to age 65 will develop skin cancer at least once.

The most common warning sign of skin cancer is a change in the appearance of the skin, such as a new growth or a sore that will not heal.

There are three main types of skin cancers:

* Squamous Cell Carcinoma

The top layer of the epidermis is mostly made up of flat, scale-like cells called squamous cells. Approximately 16% of skin cancers begin in this layer, and are called squamous cell carcinoma. They usually arise from sun exposure, but can appear on skin that has been burned, damaged by chemicals, or exposed to x-rays.

* Basal Cell Carcinoma

Under squamous cells, in the lower epidermis are round cells known as basal cells. About 80% of skin cancers arise from this layer in skin that has been exposed to the sun, and are called basal cell carcinoma. Basal cell carcinomas most often form on the head and neck.

* Melanoma

The deepest layer of the epidermis contains scattered cells called melanocytes, which produce the melanin that gives skin color. Melanoma starts in melanocytes, and it is the most serious of the three cancer types. For more information, see the summary on melanoma.

Basal cell and squamous cell cancers are known as non-melanoma skin cancers, to distinguish them from melanoma, which is much more dangerous. Basal cell carcinoma grows slowly and seldom spreads (metastasizes) to other parts of the body. Squamous cell carcinoma also rarely spreads, but is more likely to do so than basal cell carcinoma.

As we well know, there are many kinds of cancer; unfortunately they all come about because of the out-of-control growth of abnormal cells.

Basal cell carcinoma is the most common form of skin cancer. The second most common type of skin malignancy is squamous cell carcinoma. Although these 2 types of skin cancer are the most common of all malignancies, they account for less than 0.1% of patient deaths due to cancer. Both of these types of skin cancer are more likely to occur in individuals of light complexion who have had significant exposure to sunlight, and both types of skin cancers are more common in the southern latitudes of the Northern hemisphere.The overall cure rate for both types of skin cancer is directly related to the stage of the disease and the type of treatment used However, since neither basal cell carcinoma nor squamous cell carcinoma are reportable diseases, precise 5-year cure rates are not known. Although basal cell carcinoma and squamous cell carcinoma are by far the most frequent types of skin tumors, the skin can also be the site of a large variety of malignant neoplasms. These other types of malignant disease include malignant melanoma, cutaneous T-cell lymphomas (mycosis fungoides), Kaposi’s sarcoma extramammary Paget’s disease, apocrine carcinoma of the skin, and metastatic malignancies from various primary sites.

Basal cell carcinoma

Basal cell carcinoma is at least 3 times more common than squamous cell carcinoma in non- immuno compromised patients. It usually occurs on sun exposed areas of skin, and the nose is the most frequent site. Although there are many different clinical presentations for basal cell carcinoma, the most characteristic type is the asymptomatic nodular or nodular ulcerative lesion that is elevated from the surrounding skin and has a pearly quality and contains telangiectatic vessels. It is recognized that basal cell carcinoma has a tendency to be locally destructive. High-risk areas for tumor recurrence include the central face (periorbital region, eyelids, nasolabial fold, nose-cheek angle), postauricular region, pinna, ear canal, forehead, and scalp. A specific subtype of basal cell carcinoma is the morphea-form type. It typically appears as a scar-like, firm plaque and because of indistinct clinical tumor margins, it is difficult to treat adequately with traditional treatments.

Squamous cell carcinoma

Squamous cell tumors also tend to occur on sun-exposed portions of the skin such as the ears, lower lip, and dorsa of the hand. However, squamous cell carcinomas that arise in areas of non-sun-exposed skin or that originate de novo on areas of sun-exposed skin are prognostically worse since they have a greater tendency to metastasize. Chronic sun damage, sites of prior burns, arsenic exposure, chronic cutaneous inflammation as seen in long standing skin ulcers, and sites of previous x-ray therapy are predisposed to the development of squamous cell carcinoma.

Actinic keratosis

Actinic keratoses are potential precursors of squamous cell carcinoma. These typical red scaly patches usually arise on areas of chronically sun-exposed skin, and are likely to be found on the face and dorsal aspects of the hand. Although the vast majority of actinic keratoses do not become squamous cell carcinomas, it is thought that as many as 5% of actinic keratoses will evolve into this locally invasive carcinoma. Due to this premalignant potential, the destruction of actinic keratoses is advocated.