Our San Antonio - Stone Oak location has closed. Dr. Petr will now see all patients at U.S. Dermatology Partners San Antonio.

About Skin Cancer

Our clinic is dedicated to making sure all of our patients have a clear understanding of skin cancer, its causes and risks, as well as how to prevent and treat it.

Overview of Skin Cancer

If you or someone close to you has been diagnosed with skin cancer, basic information about the disease can be helpful in planning and understanding your treatment. When caught and treated early, 99% of skin cancers can be cured.

What Is Skin Cancer?

While normal skin cells grow, develop, and die in predictable cycles, skin cancer develops when skin cells grow out of control. Instead of dying, the damaged DNA within skin cancer cells causes them to continue growing and produce more abnormal cells. They also tend to invade other tissues. Skin cancer is the most common type of cancer in the US.

Causes of Skin Cancer

The primary cause of skin cancer is exposure to the ultraviolet (UV) light which damages the DNA with repeated exposure. People with chronic exposure to UV light, whether in the outdoors or in tanning booths, are at increased risk of developing skin cancer. The World Health Organization recently elevated tanning beds to its highest cancer risk category, the same rating it gives to cigarettes. Immuno-suppressed patients, such as organ transplant recipients or patients with chronic lymphocytic leukemia (CLL) are at greatly increased risk as well, because their immune systems are not as capable of warding off cancerous cells.

Types of Skin Cancer

The skin is made up of several types of cells which can be affected by distinct types of skin cancer. The 3 most common types of skin cancer, which together make up approximately 99% of diagnosed cases, are basal cell carcinoma, squamous cell carcinoma, and melanoma.  This section provides general descriptions of each type of skin cancer. In actuality, skin cancer can take on many variations and characteristics.

Basal Cell Carcinoma

As the most common type of skin cancer, basal cell carcinoma accounts for about 80% of all diagnosed skin cancers. It begins in the basal cells, which are skin cells located in the lowest layer of the epidermis. This type of cancer can look like a sore that doesn’t completely heal, a shiny bump, or a reddish, irritated portion of the skin in an area that is exposed to the sun, such as the head, ears, face, shoulders and chest. It usually progresses slowly and does not tend to spread to other areas of the body (metastasize). Early detection and treatment can prevent basal cell carcinoma from spreading to surrounding tissue.

Squamous Cell Carcinoma

Potentially more aggressive than basal cell carcinoma, squamous cell carcinoma forms just beneath the surface of the skin in the squamous layer. While this second most common type of skin cancer often develops on sun-exposed areas, it can develop on other areas of the body like the mucous membranes and genitals. It often looks like a thick, rough, scaly patch or a bump. The National Cancer Institute estimates that in 2010, almost 1000 people will die of cutaneous squamous cell carcinoma in the US.


The most dangerous of the common forms of skin cancer is melanoma. While it accounts for only about 3% of skin cancer cases, melanoma is responsible for over 75% of skin cancer-related deaths. It is estimated that almost 9000 people in the US alone will die due to melanoma in 2010. Melanoma originates in pigment-producing cells called melanocytes, which give the hair, skin, and eyes their color. Melanomas are usually black or brown, and often develop in a mole or take on the appearance of a new mole. If identified early, cure rates for melanoma are quite high. Once melanoma spreads to other parts of the body, cure rates are significantly reduced.

Symptoms & Diagnosis

While it’s important to have a dermatologist examine any suspicious areas, being aware of the signs of skin cancer can help you determine when you should seek a professional opinion. Skin cancer signs differ between the various types. Fortunately, most skin lesions are not skin cancers, but a dermatologist is most qualified to make a definite diagnosis.

Basal Cell Carcinoma

Basal cell carcinoma is the most common type of skin cancer. See skin cancer photos.

Where to watch:
Basal cell carcinoma often appears on areas most exposed to the sun such as the head, face, ears, neck, upper back, hands, and arms.

What to look for:
It can look like a small, pearly, translucent bump, an area of thickened scar tissue, or a red, scaly patch. They can often bleed, crust over, but not completely heal.

Squamous Cell Cancer

While people with light skin, hair, and eyes have the greatest risk of developing squamous cell carcinoma, chronic sun exposure increases anyone’s risk as well. It differs primarily from basal cell carcinoma in its ability to spread into the lymph nodes and internal organs.

Where to watch:
Squamous cell carcinoma (SCC) often appears on the scalp, face, ears, lips, hands, and lower legs.

What to look for:
The early stages of squamous cell skin cancer can appear as a red, scaly, flat patch, or a scaly bump. Sometimes, rapidly growing SCCs can be quite tender to the touch. The majority of these, however, are pain-free.


Melanoma is not the most common type of skin cancer, but it is one of the most dangerous. Only about a third of melanomas arise from previously-existing moles. The rest of them arise from an otherwise normal-appearing area of skin.

Where to watch:
Melanoma can develop anywhere on the body. In men, it’s most common on the chest, abdomen, or back; in women, it’s most common on the lower legs.

What to look for:
Some of the warning signs for melanoma include:

  •  A dark spot that appears suddenly next to or within an existing mole.
  • An existing mole changes in the color or size.
  • An existing mole begins crusting, oozing, or bleeding.
  • Pigment spreads from the border of a mole into surrounding skin.
  • A mole becomes tender, painful, or itchy.

Skin Cancer Diagnosis

If you notice a suspicious change on your skin, it’s important to see a dermatologist for a skin cancer screening as soon as possible. Examining your skin on a monthly basis is the best way to catch skin cancer as early as possible. Pay attention to any changes. Get to know the pattern of your moles, scars, spots, freckles, and other marks on your skin so you can detect any changes. Early diagnosis and treatment increase your chances of curing the cancer.

The most common way to diagnose skin cancer is through a biopsy. The dermatologist will numb the area, then remove all or a portion of the suspicious area. The tissue is usually sent to a lab to be examined under a microscope by a dermatopathologist. Your doctor will want to know when you first noticed the change in your skin, your symptoms, and your history of sun exposure.

Skin Cancer FAQs

If you are interested in Mohs surgery, it’s likely you also want to know more about skin cancer. We have provided answers to several common questions about how to spot and prevent skin cancer below.

What is basal cell cancer and what does it look like?

Basal cell carcinoma is the most common type of skin cancer. It usually appears on sun-exposed areas as a blemish that won’t heal or a persistent, pearly, shiny bump. The area may bleed with minor trauma. There are several other presentations including one that appears like a red, rough patch. Sometimes, they are mistaken for pimples, cysts, or rashes. See skin cancer photos.

Basal cell carcinoma almost never spreads to the lymph nodes or internal organs, except under rare circumstances. However, it can invade and destroy the immediately surrounding tissue and cause deformity if left unchecked.

What is squamous cell cancer and what does it look like?

Squamous cell carcinoma (SCC) is the second most common type of skin cancer. It also commonly arises on areas that are chronically exposed to the sun, such as the face, scalp, neck, upper back, and arms. It often appears as a hard, scaly bump or scaling patch and may be mistaken for a wart or patch of dry skin. See skin cancer photos.

Squamous cell carcinoma can occasionally spread into the lymph nodes and internal organs. This occurs more often with large, aggressive squamous cell carcinomas or rapidly-growing tumors on the ears, scalp, lips or genitalia. An increased risk of spread is also seen in patients that are immunosuppressed, such as organ transplant patients, or those with chronic lymphocytic leukemia (CLL), or in tumors that have recurred after previous treatment.

What is melanoma and what does it look like?

Melanoma is the most deadly of the common forms of skin cancer, but has an excellent prognosis if it is caught early.

Though melanoma may occur anywhere on your skin, it is found most often on the legs of women or the backs of men. This type of skin cancer often occurs in moles. It is usually a brown to black lesion which is not uniform in border, color or surface. Melanomas on chronically sun-damaged skin like the face may appear like a brown patch or freckle with irregular color.

What is actinic keratosis and what does it look like?

Actinic (solar) keratosis is the most common type of pre-cancer and results from chronic, cumulative sun exposure. Actinic keratosis looks like a scaly patch of dry skin, either flesh-colored or pink, which occurs on sun-exposed areas such as the head and neck, arms, chest and legs. Actinic keratoses should be treated early, as they can lead to squamous cell carcinoma.

Can I get skin cancer anywhere on my body?

While skin cancers usually appear on skin that has been chronically exposed to the sun (like the head, neck, arms, and chest), you can get skin cancer anywhere – even on skin that has rarely or “never” been exposed to the sun (for example, the genitals).

What can I do to protect myself from skin cancer?

The damage that your skin has already received from the sun cannot be completely reversed. However, several precautions can be taken to reduce your risk of developing further skin cancers:

  •  Minimize sun exposure from 10:00 AM to 4:00 PM when the sun’s rays are the strongest. If you enjoy outdoor activities such as golfing, gardening, running, walking, or boating, try to schedule them outside of these “peak sun hours.”
  • Apply a sunscreen with an SPF of 30 or greater at least one half hour before going outdoors and reapply as directed on the product label. Look for products containing avobenzone, titanium dioxide, or zinc oxide. These products have the highest chance of providing broad spectrum protection, blocking UVA and UVB rays. Choose a cream-based sunscreen if you have dry skin, and a gel-based, or non-comedogenic formula if you have oily or acne-prone skin. Choose a “very water resistant” formula if you will be sweating or in water; however, remember that even these must be reapplied every 80 minutes. If the ears or portions of the scalp are exposed due to short or thinning hair, remember to apply sunscreen to these areas as well.
  • Protect your lips with lipstick or a lip balm containing sunscreen.
  • Wear protective clothing, including a long-sleeved shirt, wide-brimmed hat and ultraviolet blocking sunglasses.
  • Avoid use of the UV beds at tanning salons.
  • Make sure to use sunscreen on overcast days. The ultraviolet rays can be as damaging to your skin on cloudy, hazy days as they are on sunny days.
  • Use a sunscreen while at lower latitudes or high altitudes. The sun is stronger near the equator and at high elevations, where the sun’s rays strike the earth most directly.
  • If you need a little “color,” use a sunless tanning lotion or get a spray tan.

Will my cancer come back (recur)?

The goal of Mohs surgery is to remove your skin cancer while preserving your normal healthy surrounding skin. The cure rate for Mohs skin cancer surgery is very high, even for the most difficult tumors. The cure rate is up to 99% for new skin cancers and 95% for recurrent skin cancers (those which have been treated in the past and have come back.) While no method can guarantee a cure 100% of the time, appropriately and correctly performed Mohs surgery provides the highest possible cure rate for most tumors.

Will I develop more skin cancers?

Studies have shown that once you develop a skin cancer, there is an increased risk of developing others in the years ahead. For this reason, it is important for you to continue seeing your primary dermatologist at regularly scheduled intervals, and to schedule an appointment if you are concerned about new or changing growths on your skin.

You can reduce your risk of developing more skin cancers by protecting your skin from further sun damage, but continued vigilance on your part is required (along with scheduled visits to your dermatologist) to help detect further skin cancers at an early stage.