The Skin Cancer Learning Center

What Is Skin Cancer?

Skin Cancer is very common and affects millions of American children and adults each year. Prevention and detection are the keys against skin cancer. There are three common types of skin cancer: Squamous cell carcinoma, Basal Cell carcinoma, and Melanoma. Lesions called Actinic Keratosis are sometimes referred to as “precancers”, but these are actually the earliest stages of squamous cell carcinoma.

Actinic Keratosis And Squamous Cell Carcinoma

What Is It?

Squamous cell carcinoma is the most common skin cancer. It arises from the epidermis and resembles the squamous cells that comprise most of the upper layers of skin. Squamous cell skin cancers may occur on all areas of the skin including the mucous membranes of the lips and genitals, but are most common in areas exposed to the sun.

An Actinic Keratosis (AK), also known as a solar keratosis, is a squamous cell carcinoma “in-situ.” “In situ” is Latin and means “in one site” or “localized.” It is the earliest form of squamous cell carcinoma. It is a scaly, crusty bump that arises on the skin surface. Its growth is limited to the top layer of skin (epidermis) only. Therefore, it is “in situ”. The lesion may be light or dark, tan, pink, red, or a combination of these colors. The scale or crust is, dry, and rough, and is often recognized by touch rather than sight. It may itch or feel like a thorn pricking the skin. It can also become inflamed and surrounded by redness. An AK is most likely to appear on the face, ears, scalp, neck, backs of the hands and forearms, shoulders, and lips - the parts of the body most often exposed to sunshine. They may be flat and pink or raised and rough.

Invasive squamous cell carcinomas appear as thickened scaly plaques or dome shaped nodules. The lesions may be red and inflamed, painful, and may have a central ulcer. They may also be volcano-like, with the central crater filled with hard dead skin.

What Causes It?

Chronic exposure to sunlight causes most cases of squamous cell carcinoma. That is why tumors appear most frequently on sun-exposed parts of the body. The rim of the ear and the lower lip are especially vulnerable to the development of these cancers.

Squamous cell carcinomas may also occur where skin has suffered certain kinds of injury: burns, scars, long-standing sores, sites previously exposed to X-rays or certain chemicals (such as arsenic and petroleum by-products). In addition, medications or diseases that suppress the immune system may encourage development of squamous cell carcinoma.

Occasionally, squamous cell carcinoma arises spontaneously on what appears to be normal, healthy, undamaged skin. Some researchers believe that a tendency to develop this cancer may be inherited.

Why Is It Dangerous?

Actinic Keratosis can usually be eliminated without requiring biopsy or surgery. They are not life-threatening if they are detected and treated in the early stages. However, if left untreated, they can become invasive squamous cell carcinomas. If you have actinic keratosis, it indicates that you have sustained sun damage and could develop any kind of skin cancer, not just squamous cell carcinoma. People may also have up to 10 times as many subclinical (invisible) lesions as visible, surface lesions.

Invasive squamous cell carcinomas penetrate the underlying tissues. They may spread (metastasize) to distant tissues and organs. When this happens, they can be fatal. Squamous cell carcinomas that metastasize most often arise on sites of chronic inflammatory skin conditions or on the mucous membranes or lips.

Back to top

Basal Cell Carcinoma

What Is It?

Basal cell carcinoma (BCC) arises in the basal cells, which are at the bottom of the epidermis (outer skin layer). Until recently, those most often affected were older people, particularly men who had worked outdoors. The number of new cases increases each year, and the average age of onset has steadily decreased. More women are getting BCCs than ever before.

What Causes It?

As with squamous cell carcinoma, chronic exposure to sunlight is the cause of almost all basal cell carcinomas. They occur most frequently on sun exposed parts of the body. Rarely, however, tumors develop on non-exposed areas. In a few cases, basal cell carcinomas have been known to occur in areas that have been damaged by contact with toxic chemicals or scarred by burns, radiation, vaccinations, or even tattoos.

Here are the five warning signs of Basal Cell Carcinoma:

  1. An Open Sore that bleeds, oozes, or crusts and remains open for three or more weeks. A persistent, non-healing sore is a very common sign of an early basal cell carcinoma.

  2. A Reddish Patch or irritated area, frequently occurring on the chest, shoulders, arms, or legs. Sometimes the patch crusts. It may also itch or hurt. At other times, it persists with no noticeable discomfort.

  3. A Shiny Bump or nodule, that is pearly or translucent and is often pink, red, or white. The bump can also be tan, black, or brown, especially in dark-haired people, and can be confused with a mole.

  4. A Pink Growth with a slightly elevated rolled border and a crusted indentation in the center. As the growth slowly enlarges, tiny blood vessels may develop on the surface.

  5. A Scar-like Area which is white, yellow or waxy, and often has poorly defined borders. The skin itself appears shiny and taut.


The five most typical characteristics of basal cell carcinoma are shown below. Frequently, two or more features are present in one tumor. In addition, basal cell carcinoma sometimes resembles non-cancerous skin conditions such as psoriasis or eczema. Only a trained skin, specialist can decide for sure.

Back to top


What Is It?

Melanoma is the most serious form of skin cancer. Even so, if diagnosed and removed while it is still thin and limited to the outermost skin layer, it is almost 100% curable. Once the cancer advances and metastasizes (spreads) to other parts of the body, it is hard to treat and can be deadly. During the past 10 years the number of cases of melanoma has increased more rapidly than that of any other cancer. Over 51,000 new cases are reported to the American Cancer Society each year, and it is probable that a great many more occur and are not reported.

Melanoma is a cancer that originates in melanocytes, which are the cells which produce the pigment (melanin) that colors our skin, hair, and eyes and is heavily concentrated in most moles. The majority of melanomas, therefore, are black or brown. However, melanomas occasionally stop producing pigment. When that happens, the melanomas may no longer be dark, but are skin-colored, pink, red, or purple.

Melanomas have classically been given different names based upon presumed growth characteristics based upon the appearance of tumor sections examined under the microscope. This is no longer a useful concept. Terms such as superficial spreading melanoma, lentigo malignant melanoma, acral lentiginous melanoma, and nodular melanoma give no insight into the critical question of the location of the tumor within the epidermis, its degree of penetration into adjacent deeper tissues, or its tendency to metastasis.

Just as with squamous cell carcinoma, melanoma will be described as either in situ or invasive. “In situ” is Latin and means “in one site” or “localized.” Melanoma in situ occupies only the epidermis, the top layer of the skin. Invasive melanomas are the more serious, as they have penetrated more deeply into adjacent tissue and may have metastasized.

The ABCD’s of Moles & Melanoma

Most people have a number of brownish spots on their skin - freckles, birthmarks, moles. Almost all such spots are typical, but some may be melanoma. The ABCD’s of melanoma are as follows:



Most early melanomas are asymmetrical: a line through the middle would not create matching halves. Common moles are round and symmetrical.


The borders of early melanomas are often uneven and may have scalloped or notched edges. Common moles have smoother, more even borders.


Common moles usually are a single shade of brown. Varied shades of brown, tan, or black are often the first sign of melanoma. As melanomas progress, the colors red, white and blue may appear.


Common moles are usually smaller then the size of a pencil eraser (about 6mm, or 1/4 inch, in diameter). Melanoma may be larger.


If You Can Spot It, You Can Stop It

Along with a yearly skin exam by a doctor, self-examination of your skin once a month is the best way to detect the early warning signs of skin cancer. Look for a new growth or any skin change.

What you’ll need:

A bright light, a full-length mirror, a hand mirror, two chairs or stools, and a blow-dryer.

  1. Examine head and face, using one or both mirrors. Use blow-dryer to inspect scalp.

  2. Check hands, including nails. In full-length mirror, examine elbows, arms, underarms.

  3. Focus on neck, chest, and torso. Women: Check under breasts.

  4. With back to the mirror, use hand mirror to inspect back of neck, shoulders, upper arms, back, buttocks, legs.

  5. Sitting down, check legs and feet, including soles, heels, and nails. Use hand mirror to examine anus and genitals.

If you detect any of the warning signs of skin cancer, Polley Clinic can help you with all phases of diagnosis and treatment.