The most common of all human cancers occur on the skin . These tumors are not always malignant, meaning that they are rapidly growing and metastatic, thus spreading to other parts of the body. Often skin tumors are benign and in some cases spontaneously regress over time. Examples of benign tumors are warts , moles (or nevi), seborrheic keratosis, keratoacanthoma , and the often premalignant actinic keratosis . Malignant disorders include basal cell carcinoma, squamous cell carcinoma and malignant melanoma.

Early detection is very important and any warning signs should be evaluated by a physician. Often, warning signs of skin cancer can be seen in moles. Examine moles with the following signs in mind:

A symmetry
B orders that are irregular
C olor variations
D iameter larger than a pencil's eraser

Basal Cell Carcinoma
This is the most frequent type of skin cancer, with hundreds of thousands of cases each year. It tends to occur in older persons. Lesions almost always occur in sun exposed or sun burned regions. This cancer is slow growing and rarely metastasizes (spreads). Treatment is necessary due to the localized damage caused by this cancer . This cancer of keratinocytes is usually smooth with a pearly border and may be pigmented with a ulceration in the center of the lesion. Treatment is by surgical removal, freezing or local chemotherapy .

Squamous Cell Carcinoma
This cancer can affect both the skin and mucous membranes. It often occurs in sun exposed or burned areas. Tar derivatives such as those in tobacco smoke or other carcinogens and chronic radiation exposure are predisposing factors. Immunosupression in transplant patients makes them at greater risk of developing these lesions. The lesions appear as rough scaly nodules that can ulcerate and metastsize. The cancerous keratinocyte cells often extend down through the basement membranem zone into the dermis. Surgical removal is the treatment of choice, with a check and removal of enlarged draining lymph nodes for all but the smallest of lesions.

Malignant Melanoma
This cancer has been increasing in incidence in caucasians and now accounts for very significant morbidity and mortality. It has been estimated that in the U.S. an individual's lifetime risk of having malignant melanoma is 1 in 75. Pigment producing cells, melanocytes, are the originating cells of this type of cancer. Risk of this cancer increases with increased sun exposure , particularly childhood esposure including sunburns . Heredity, congenital or dysplastic nevi, and fair skin are also risk factors. These lesions are known for their invasiveness and metastatic behavior. Prognosis is dependent on the depth of invasion of the tumor. Therefore, early detection and removal are critical. All moles (nevi) should be inspected regularly for irregular borders and surfaces or a change in color.

Warts/Papillomas
Warts are raised, well-defined benign growths with an irregular gray or pink surface.  The warts seen on the hands are called verruca vulgaris or the common wart. The human wart virus is transmitted by direct contact, but may be autoinnoculated by razors in shaving , for example. Warts almost always regress spontaneously but sometimes they are removed by freezing, by the use of salicylic acid plasters, or OTC wart removal treatments. Plantar warts, verruca plantaris, tends to grow on the soles of the feet. Warts on the feet are painful because of the irritation of walking. These warts tend to grow inwardly.

Condylomata acuminata are large, pink or purple lesions located primarily in warm moist anal or genital areas. Although commonly known at venereal warts, they do not necessarily arise from sexual contact.