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Skin Cancer Module: Practice Exercises

	See Also... Skin Cancer Home Module 9: Know Your Skin Type Module 11: Epidemiology of Melanoma Skin Cancer Glossary
	On this Page Objective The Three Types of Skin Cancer Where Do Skin Cancers Occur? Exercises

Module 10: Skin Cancers

Objective: Understand the different types of skin cancer.

In recent years, more than 40 percent of all cancers in the United States have been skin cancers. The major cause of skin cancer is exposure to ultraviolet (UV) rays from the sun.

Skin cancer is common. It can kill or cause bad scarring. But you can prevent it.

The Three Types of Skin Cancer

There are three main types of skin cancer:

• basal cell carcinoma
• squamous cell carcinoma
• malignant melanoma

Basal and squamous cell carcinomas are often called "non-melanoma skin cancers." They make up 95 percent of skin cancers. Melanoma only occurs in 5 percent of skin cancer cases. But melanoma causes the most deaths from skin cancer.

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1. Basal Cell Carcinoma

This type of cancer begins in the basal cell layer, the lowest layer of the epidermis. About 80 percent of all skin cancers are basal cell carcinomas. They usually begin on areas exposed to the sun, such as the face. This type of cancer develops slowly. It usually doesn't spread to other parts of the body. Too much exposure to the sun as a child or an adult can lead to basal cell carcinomas later in life. This can happen even if you never had a sunburn.

Basal Cell Carcinoma Images
Courtesy of the American Academy of Dermatology

To see additional images and learn more about basal cell carcinoma, click on http://matrix.ucdavis.edu/tumors/tradition/bce.html*.

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2. Squamous Cell Carcinoma

This type of cancer begins in the top layer of the skin. About 15 percent of all skin cancers are squamous cell carcinomas. They usually appear on areas exposed to the sun, such as the ears, neck, lips, face, and hands. This type of cancer is more likely to spread to other parts of the body than basal cell carcinoma. Prevention and early detection greatly lower the risk of this cancer.

Squamous Cell Carcinoma Images
Courtesy of the American Academy of Dermatology

Actinic Keratoses
Squamous cell carcinomas can begin as rough, scaly, pinkish patches of skin. These are called actinic keratoses. Actinic keratoses are not cancer. But they may become squamous cell carcinomas over time if they are not treated. They have been directly linked to long-term sun exposure. Actinic keratoses are fairly common in older people. They are usually found on the face and head, backs of hands, forearms, and chest. Dermatologists often remove actinic keratoses by freezing them with liquid nitrogen. Sometimes they apply other types of treatments to the skin instead. Using sunscreen can prevent actinic keratoses.

To see images and learn more about actinic keratoses, click on: http://www.skincarephysicians.com/actinickeratosesnet/ or http://matrix.ucdavis.edu/tumors/tradition/ak-gallery.html.*

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3. Melanoma

This type of cancer begins in the melanocytes, the skin cells that make pigment. About 5 percent of all skin cancers are melanomas. Melanoma is the most dangerous type of skin cancer. This is because it can spread easily to other parts of the body if not detected early.

The major cause of melanoma is too much sunlight. This is especially true when sunburn and blistering occur. We get as much as 80 percent of our sun exposure before the age of 18. So it is important to keep from burning and tanning when we are young. Research studies show that people who get three or more blistering sunburns before they are 20 years old have a much higher risk for malignant melanoma. They are five times more likely to develop the disease than those who have never had a sunburn.

Melanoma is the 6th most common cancer in males. It is the 7th most common cancer in females. Even people under 25 years old can get melanoma and other skin cancers. Each year, malignant melanoma kills about 100,000 people worldwide. (This included 7,000 Americans in 1997.) Melanoma is the most common cancer among people 25 to 29 years old.

Malignant Melanoma Images
Courtesy of the American Academy of Dermatology

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The ABCDs of Melanoma
Courtesy of the American Academy of Dermatology

Asymmetry - Meaning one half is different than another. Draw an imaginary line through the middle of the lesion, either up and down or side to side. Are the two sides the same size and shape (symmetric)? Melanomas are usually asymmetric.
Border Irregularity - The edge, or border, of melanomas are usually ragged, notched, or blurred.
Color - Benign moles can be any color, but a single mole will be only one color. Melanoma often has a variety of hues and colors within the same lesion.
Diameter - Melanomas continue to grow, while moles remain small. Is the lesion larger than a pencil eraser (6mm)?

To see additional images and learn more about malignant melanomas, click on http://matrix.ucdavis.edu/tumors/tradition/gallery-scc.html.*

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Where Do Skin Cancers Occur?

Both melanoma and non-melanoma skin cancers can occur anywhere on the body. But basal and squamous cell cancers more often appear in areas that are exposed to the sun often over many years. These include the face, head, neck, arms, and back of hands of people who spend much time outside. (Some examples are farmers, sailors, and outdoor laborers.) In contrast, melanomas are more likely to occur on areas of the body that are exposed to sun intensely on and off. These include the back and chest in men, and the backs of lower legs in women. These are especially common sites of melanoma in people who sunbathe or vacation in sunny places.

Percentage of cases with basal cell carcinoma of the skin, by anatomic site, among white males and white females in the United States (1977-1978)

*Not otherwise specified
Source: Cancer Epidemiology and Prevention, 2nd. Ed. Oxford University Press: Oxford, New York. 1996.

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Percentage of cases with squamous cell carcinoma of the skin, by anatomic site, among white males and white females in the United States (1977-1978)

*Not otherwise specified
Source: Cancer Epidemiology and Prevention, 2nd. Ed. Oxford University Press: Oxford, New York. 1996.

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Exercises

A. Seeing What Skin Cancer Looks Like

Step 1: Click on: http://www.meddean.luc.edu/
lumen/MedEd/medicine/dermatology/title.htm.*
Step 2: Click on "A Skin Cancer and Benign Tumor Image Atlas." You will see a list of skin cancer and tumor types to choose from.
Step 3: Click on each of the three skin cancer types: Basal Cell Carcinoma, Squamous Cell Carcinoma, and Malignant Melanoma. View a few images of each type.
Step 4: For more examples of what melanoma can look like, go to http://www.skincarephysicians.com/melanomanet/skin_lesions.htm.*

B. Comparing Rates of Different Cancers

Graph the following data on a bar graph. Your graph should compare the number of cases and the number of deaths for each type of cancer.

(This information is from SunSmart, "Types of Skin Cancer.")

Questions

1. Which cancer is the most common? Which is the least common?
   
   
2. Which cancer seems to be the least treatable? Which seems to be the most treatable?
   
    
3. Give a possible reason for the high rates of basal and squamous cell skin cancers.
   
   
4. Of all types of cancer in the table above, at what percent rate does skin cancer occur? Use this formula to find the rate:
   
   (NMSC+Melanoma/Total of all cancers x 100)
   
   In this formula, NMSC stands for "non-melanoma skin cancer." This term refers to basal and squamous cell cancers.

See Answers to Questions

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* Links to non-Federal organizations are provided solely as a service to our users. Links do not constitute an endorsement of any organization by CDC or the Federal Government, and none should be inferred. The CDC is not responsible for the content of the individual organization Web pages found at these links.

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