Over the course of your lifetime, the DNA of a single gene may be damaged several billion times. Therefore, a single "injury" is not the cause of cancer. Something much more significant must occur. About 20 human genes have been identified that, when altered, can lead to the more common types of cancer.

*Oncogene - a gene that causes cancer or other uncontrolled cell division.
*Proto-oncogene - a gene that, when altered by mutation, becomes an oncogene.
*Anti-oncogene - a gene that suppresses tumor growth.

• Formaldehyde

• Benzene

• Radiation

• Other risk factors

• Tobacco

• Some viruses

• Other chemicals

Types of tumors:

*Benign: the tumor cells remain attached to the parent tumor.

Benign comes from the Latin word benignus, meaning "good".

*Malignant: the tumor cells metastasize.

Cells metastasize when they break away from the parent tumor and spread to other parts of the body, where they begin forming new tumors. Malignant tumors are categorized by the types of tissues they affect:

*Carcinoma - occurs in skin and nerve cells.
*Sarcoma - occurs in bone and muscle cells.
*Lymphoma - occurs in lymph cells.

• Squamous cell carcinoma - SCC
arise from flattened (squamous) cells in the outer layer.

SCC's and BCC's are often lumped together as non-melanoma skin cancers - NMSC's.

Chronic exposure to sunlight is the cause of almost all basal cell carcinomas, which occur most frequently on exposed parts of the body like the face, ears, neck, scalp, shoulders, and back. Rarely do tumors develop on non-exposed areas.

Although the number of new cases of BCC has increased sharply each year in the last few decades, the average age of onset of the disease has steadily decreased.

In a few cases, contact with arsenic, exposure to radiation, and complications of burns, scars, vaccinations, or even tattoos are contributing factors.

Squamous cell carcinoma, SCC, is the second most common cancer of the skin. Squamous cell carcinoma is a tumor that arises in the outer layer of the skin (the epithelium). More than 250,000 new SCC's are diagnosed every year in the U.S.

A SCC generally appears as a crusted or scaly area of the skin, with a red, inflamed base. They can present as a growing tumor, a non-healing ulcer, or just as a crust.

Ultraviolet light exposure (through the sun or tanning beds) greatly increases the chance of developing skin cancer. Persons with light skin who sunburn easily are at highest risk, although anyone can get squamous cell carcinoma. With increasing age, the risk of developing skin cancer grows. Heavy sun exposure and severe sunburns as a child may especially increase the likelihood of skin cancer.

SCC's are common in sun-exposed areas like the face, neck, and arms. The scalp, backs of hands, and ears are especially common. However, SCC can occur anywhere on the body, even on the lips, inside the mouth, and on the genitalia.

Usually these skin cancers are locally destructive. If left untreated, squamous cell carcinoma can destroy much of the tissue surrounding the tumor and may result in the loss of a nose or ear. In certain aggressive types of SCC's, especially those on the lips and ears, or those that are left untreated, the tumor can spread to the lymph nodes and other organs, resulting in approximately 2,500 deaths each year in the United States.
 
Malignant melanoma, MM, 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 malignant tumor that originates in melanocytes, the cells which produce the pigment melanin that colors our skin, hair, and eyes and is heavily concentrated in most moles.

MM's are usually small brown-black or larger multicolored patches, plaques or nodules with irregular outline. They may crust on the surface or bleed. Many of them may arise in pre-existing moles.

In situ melanomas occupy only the uppermost part of the epidermis, the top layers of the skin.

Invasive melanomas are the more serious, as they have penetrated more deeply into the skin and may have traveled from the original tumor through the body.

Melanomas fall into four basic categories. Three of them begin in situ and sometimes become invasive; the fourth is invasive from the start.

• Superficial spreading melanoma is by far the most common type, accounting for about 70 percent of all cases. This melanoma travels along the top layer of the skin for a fairly long time before penetrating more deeply.

The first sign is the appearance of a flat or slightly raised discolored patch that has irregular borders and is somewhat geometrical in form. The color varies, with areas of tan, brown, black, red, blue, or white. Sometimes an older mole will change in these ways, or a new one will arise. The melanoma can be seen almost anywhere on the body, but is most likely to occur on the trunk in men, the legs in women, and the upper back in both. Most melanomas found in the young are of the superficial spreading type.

• Lentigo maligna melanoma is similar to the superficial spreading type, as it also remains close to the skin surface for quite a while, and usually appears as a flat or mildly elevated mottled tan, brown, or dark brown discoloration. However, lentigo maligna melanoma easily becomes invasive.

This type of in situ melanoma is found most often in the elderly, arising on chronically sun-exposed, damaged skin on the face, ears, arms, and upper trunk.

• Acral lentiginous melanoma, also spreads superficially before penetrating more deeply. It is quite different from the others, though, as it usually appears as a black or brown discoloration under the nails or on the soles of the feet or palms of the hands.

This type of melanoma is sometimes found in dark-skinned people. It is the most common melanoma in African-Americans and Asians, and the least common among Caucasians.

• Nodular melanoma, unlike the other three types, is usually invasive at the time it is first diagnosed. The malignancy is recognized when it becomes a bump. The color is most often black, but occasionally is blue, gray, white, brown, tan, red, or skin tone.

The most frequent locations are the trunk, legs, and arms, mainly of elderly people, as well as the scalp in men. This is the most aggressive of the melanomas, and is found in 10 to 15 percent of cases.

Atypical moles may be related to cancer but warts, generally, are not.

Leukemia - uncontrolled production of white blood cells.

Treatments for cancer:
Surgery physically removes the cancer cells from the body.
Chemotherapy chemicals taken internally to kill cancer cells.
Radiation therapy exposing the tumor to radiation to kill cancer cells.

Answer the following questions. Head your paper, Unit 5 Day 2 Cancer.

1. List and describe the three types of skin cancer.

2. List and describe types of tumors.

3. List the 5 warning signs of basal cell carcinoma.

4. What are the ABCD rules for cancer?