9.5: Cancer

Cancer is the name given to a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues.

Cancer is the second leading cause of death in the United States after Cardiovascular Disease. In 2019 in the United States, 1,752,735 new cancer cases were reported and 599,589 people died of cancer. For every 100,000 people, 439 new cases were reported and 146 people died of cancer.

Cancer has a major impact on society in the United States and across the world. Thankfully, in the United States, the likelihood of dying from cancer has dropped steadily since the 1990s. Five year survival rates for some cancers, such as breast, prostate, and thyroid cancers, now are 90 percent or better. In addition, the 5 year survival rate for all cancers combined is currently about 67 percent. According to the National Cancer Institute, the cancer death rates have decreased on average 2.3% in men and 1.9% for women from 2015 to 2019.

From 2014-2018, there has been some cancers in men and women that have decreased and some that have increased. The eight cancers that decreased in among men were lung and bronchus, larynx, urinary bladder, stomach, thyroid, colon and rectum, non-Hodgkin lymphoma, and brain and other nervous system. Pancreas, kidney and renal pelvis, and testis cancer increased in men. In women, seven cancers decreased: thyroid, ovary, colon and rectum, lung and bronchus, urinary bladder, non-Hodgkin lymphoma, and brain and other nervous system. Also in women, 7 of the 18 most common incidence rates increased including: melanoma, liver and intrahepatic bile duct, myeloma, kidney and renal pelvis, pancreas, breast, and oral cavity and pharynx. It should be noted that also during 2014-2018, cancer incident rates in people between the ages of 15-39 increased on average by 0.9%. We will look as to what factors influenced these changing trends in a little bit.

Cancer can start almost anywhere in the human body when just one of the trillions of cells changes and begins to grow uncontrollably and spread to other parts of the body. Normally, human cells grow and multiply through cell division to form new cells as the body needs them. When cells become more and more abnormal, old or damaged cells survive when they should die, and new cells form when they are not needed. These extra cells can divide without stopping and may form growths called tumors.

Tumors

Tumors can be benign or malignant. A benign tumor is not cancerous. Benign tumors do not spread to other parts of the body, also known as metastasis. Benign tumors are usually left in the body unless it is causing pain or is life threatening, such as benign tumors in the brain. When benign tumors are removed, they usually do not grow back, whereas malignant tumors sometimes do.

Malignant (cancerous) tumors spread into, or invade, nearby tissues. In addition, as these tumors grow, some cancer cells can break off and travel to distant places in the body through the blood or the lymph system and form new tumors far from the original tumor. It is important to note that not all cancers form tumors. For example, leukemia is a cancer of the blood cells that build up in the blood and sometimes in the bone marrow.

Figure \(\PageIndex{1}\): Diagram showing how cancer cells keep on reproducing to form a tumor

Figure \(\PageIndex{2}\): Diagram showing how cancer cells can detach from a tumor and spread to other parts of the body

Metastasis

In metastasis, cancer cells break away from where they first formed (primary cancer), travel through the blood or lymph system, and form new tumors (metastatic tumors) in other parts of the body. A cancer that has spread from the place where it first started to another place in the body is called metastatic cancer. As we learned earlier in this chapter, metastasis is the process by which cancer cells spread to other parts of the body.

Cancer can metastasize to several places in the body; however, it will be known by the primary site where the initial cancer cell began. For example, if a person has breast cancer that has spread to the lung, they will be determined to have breast cancer with lung metastases, not as lung cancer.

Under a microscope, metastatic cancer cells generally look the same as cells of the original cancer. Moreover, metastatic cancer cells and cells of the original cancer usually have some molecular features in common, such as the presence of specific chromosome changes.

Cancer Stages

The cancer stage refers to the extent of your cancer, such as how large the tumor is, and if the cancer has spread to other parts of your body. Almost always, a cancer is referred to by the stage it was given at diagnosis.

Stage 0

In Stage 0, abnormal cells are present but have not spread to nearby tissue. Also called carcinoma in situ, or CIS. CIS is not cancer, but may become cancer.

Stage 1, Stage 2, and Stage 3

Cancer is present. The higher the number, the larger the cancer tumor and the more it has spread into nearby tissues.

Stage 4

The cancer has spread to distant parts of the body.

Cancer Screening and Symptoms

Before learning about the various types of cancer, it is important to note that many cancers have no symptoms, rather they are asymptomatic. It is important to get annual checkups and screenings to detect cancer. For example, women should get pap tests annually and mammograms after 40 (or earlier if their doctor recommends it due to breast cancer running in their family or other factors). Men and women should get a colonoscopy every 10 years starting at age 45. People should always follow their doctor’s recommendations.

Early detection is key for cancer survival. The acronym CAUTION is a helpful reminder of the most common symptoms of cancer that you should watch out for. If you see any of the following symptoms, please make an appointment with your primary care physician as soon as possible.

Figure \(\PageIndex{3}\): CAUTION Acronym

Change in bowel or bladder habits

A sore that does not heal

Unusual bleeding or discharge

Thickening or lump in breast or elsewhere

Indigestion or difficulty in swallowing

Obvious change in wart or mole

Nagging cough or hoarseness

Types of Cancer

There are more than 100 types of cancer. Types of cancer are usually named for the organs or tissues where the cancer forms. For example, lung cancer starts in the lung, and brain cancer starts in the brain. Cancers also may be described by the type of cell that formed them, such as an epithelial cell or a squamous cell.

Skin Cancer

Did you know that the skin is the largest organ in the human body? Our skin has many purposes including protection against the heat, sun, injury, and infection. It also stores water, fat, Vitamin D, and helps us control our body temperature. Our skin consists of many layers including the epidermis. The epidermis consists of three kinds of cells: basal, squamous, and melanocytes. These three places are the three places that skin cancer occurs.

Skin cancer can occur in both men and women. It is the most common type of cancer. The main types of skin cancer include basal cell carcinoma, squamous cell carcinoma, and melanoma. Melanoma is not as common; however, it is the type of skin cancer that most people die from. It is also more likely to spread to other parts of the body compared to the other types of skin cancer. On average, melanoma occurs in 21.2 per 100,00 men and women per year. The death rate between 2017-2021 was 2 per 100,000.

Figure \(\PageIndex{4}\): Different Examples of Skin Cancer

Skin cancer has risk factors that should be taken into consideration and avoided when possible. People should limit exposure to ultraviolet radiation from the sun or artificial sunlight, such as a tanning bed. Individuals with a fairer complexion are also at higher risk for developing skin cancer. This also includes: people who do not tan or do not tan well, have freckles, are more likely to sunburn, light colored eyes, and blond or red hair. Other risk factors include having a family history of skin cancer, history of sunburns, and having many moles. Sunscreen is recommended to help prevent sunburns, which is also known as sun damaged skin.

Though not all skin cancer can be easily detectable, self checks are a helpful way to help prevent skin cancer. Often the first sign of melanoma is a change in the size, shape, color, or feel of a mole. Most melanomas have a black or black-blue area. Melanoma may also appear as a new mole. It may be black, abnormal, or “ugly looking.”

Thinking of “ABCDE” of Melanoma can help you remember what to watch for:

• Asymmetry – the shape of one half does not match the other
• Border – the edges are ragged, blurred or irregular
• Color – the color is uneven and may include shades of black, brown and tan
• Diameter – there is a change in size, usually an increase (larger than 6 millimeters or about 1/4 inch)
• Evolving – the mole has changed (in size, color, shape; it may start to itch or bleed) over the past few weeks or months

You should always consult a doctor if you have any concerns. To help prevent skin cancer while still having fun outdoors, protect yourself by seeking shade, applying sunscreen, and wearing sun-protective clothing, a hat, and sunglasses.

For more information, visit Reducing Risk for Skin Cancer.

Breast Cancer

Breast cancer can occur in both men and women. It is the second most common type of cancer in women with skin cancer being the most common. In 2024, there were an estimated 310,720 new cases of breast cancer. It has a 91.2% 5 year relative survival rate when looking from 2014-2020. Breast cancer is rare in men. Breast cancer occurs when the cells in the breast grow out of control. The type of breast cancer is determined by the type of cell that turned into cancer with the most common types being invasive ductal carcinoma and invasive lobular carcinoma (~10-15% of cases).

In most types of breast cancer, the cancer begins in the ducts of the breast, which is the tube part of the breast that carries milk to the nipple. Some other symptoms of breast cancer could include:

• New lump in the breast or underarm (armpit).
• Thickening or swelling of part of the breast.
• Irritation or dimpling of breast skin.
• Redness or flaky skin in the nipple area or the breast.
• Pulling in of the nipple or pain in the nipple area.
• Nipple discharge other than breast milk, including blood.
• Any change in the size or the shape of the breast.
• Pain in any area of the breast.

Screening through mammograms and self-exams help look for signs of cancer even before symptoms occur. Mammograms and self-exams can help identify breast cancer. Mammograms can reveal lumps and sometimes thicker connective tissues. Self-exams of the breast and underarm can help find lumps and/or thicker areas on the breast or under the arm. In men, a lump on the breast is often felt when there is breast cancer.

There are many different types of treatment for breast cancer with new treatments that are being tested through clinical trials. Some of the types of treatment include:

• Surgery
• Radiation therapy
• Chemotherapy
• Hormone therapy
• Targeted therapy
• Immunotherapy

There are side effects and it is best to discuss plans for treatment with your doctor to come up with the best treatment for you and your specific cancer.