Key terms & questions

Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body. This occurs when the normal process of new cell growth and division after old or damaged cell death doesn’t happen as it should. Instead, abnormal or damaged cells multiply and form tumors that can be cancerous (malignant) or not (benign).16 To read more about what happens, visit The National Cancer Institute’s explanation here.

In situ cancer is when abnormal cells that look like cancer cells are found only where they first formed, meaning, they have not spread to nearby tissue. It is possible that they will become cancer and spread into nearby tissue in the future. In situ cancer is sometimes also called stage 0 disease, or stage 0 cancer.27

Invasive cancer is cancer that has already spread beyond the layer of tissue it originally developed in. It grows into surrounding, healthy tissues. With melanoma, it can spread to other areas beyond the immediately surrounding tissue.28

It is not always known why certain cancers occur or why a person’s cells have grown out of control. We do know that the body normally eliminates damaged DNA (within our genes) before they become cancer, but as we age the body becomes less able to do so. These changes are called genetic changes.16 For more on this, visit The National Cancer Institute’s explanation here.

Cancer is considered a genetic disease because it is caused by changes to our genes that control how our cells function. It does not mean that all cancers are inherited,16 though some are. Having biological family members who have had cancer may put you at higher risk for certain cancers, including melanoma.11

Metastatic cancer is a cancer that has spread from the place it started to another place in the body. The process by which it does this is called metastasis. When a cancer spreads to another part of the body it is still called the original cancer. This is because, when looked at under a microscope, the metastatic cancer cells usually look the same as the original cancer cells and have some molecular features in common, like specific chromosome changes. Most people who die from cancer, die from metastatic disease.16

Ultraviolet A (UVA) has a longer wavelength. UVA affects aging. 
Ultraviolet B (UVA) has a shorter wavelength. UVB affects skin burns.

Both do harm, and these rays damage the DNA in skin cells. In turn, this produces genetic defects, also called mutations, that lead to skin cancer and premature aging. UV rays also can also damage the eyes and eyelid.17

You can greatly reduce this danger by taking protective measures, such as

  • avoiding sunburns 
  • not using a tanning bed or sun lamp 
  • seeking shade, especially between 10 am and 4 pm 
  • covering up with clothing, especially UV protective clothing and sunglasses and wide-brimmed hats 
  • using a broad-spectrum (UVA/UVB) sunscreen every day and applying 30 minutes before you go outside, reapplying every 2 hours when swimming or sweating.18

Do not use sunscreen on babies under 6 months of age.21,18 keep the Food and Drug Administration recommends keeping younger ones out of the sun between the hours of 10 am and 2 pm, and to use protective clothing if you cannot avoid having them in the sun. 18,19

Remember, a tan is sign of damaged skin.20 For more information, see the Skin Cancer Foundation’s Skin Cancer Prevention Guide and Your Daily Sun Protection Guide

There is nothing guaranteed to prevent melanoma. Most skin cancers are caused by too much exposure to UV rays. Most comes from the sun, while others come from man-made sources like tanning beds. It’s important to remember there are no safe UV rays, so anything you can do to protect yourself and loved ones from these rays is important to do. The American Cancer Society suggests that you remember to "Slip! Slop! Slap!® and Wrap”

  • Slip on a shirt 
  • Slop on sunscreen 
  • Slap on a hat 
  • Wrap on sunglasses21

To learn more about UV rays, see The American Cancer Society’s Ultraviolet (UV) Radiation web page. 
You can greatly reduce the danger by taking protective measures, such as

  • avoiding sunburn 
  • not using a tanning bed or sun lamp 
  • seeking shade, especially between 10 am and 4 pm 
  • covering up with clothing, especially UV protective clothing and sunglasses and wide-brimmed hats 
  • using a broad-spectrum (UVA/UVB) sunscreen every day and applying 30 minutes before you go outside, reapplying every 2 hours when swimming or sweating. Do not use sunscreen on babies under 6 months of age; keep the younger ones out of the sun.18  

For more information, see the Skin Cancer Foundation’s Skin Cancer Prevention Guide and Your Daily Sun Protection Guide.

It’s important to know that there is no sunscreen that can protect you completely.

What is important is to read the label and know what you are looking for to get the best protection you can.21

Recommended sunscreens: those with broad spectrum protection (UVA and UVB rays) and a sun protection factor (SPF) value of 30 or higher.21

What to know about the SPF numbers: The SPF number is the level of protection the sunscreen provides against UVB rays, which are the main cause of sunburn. This is not a measure of UVA protection. What this means is when applying an SPF 30 sunscreen correctly, you get 1 minute of UVB rays for each 30 minutes you spend in the sun. So, 1 hour in the sun wearing SPF 30 sunscreen is the same as spending 2 minutes totally unprotected. People often do not apply enough sunscreen, so their protection is less than they think.

Sunscreens labeled with SPFs as high as 100+ are available. Higher numbers do mean more protection, but it’s important to understand how this works. SPF 15 sunscreens filter out about 93% of UVB rays, while SPF 30 sunscreens filter out about 97%, SPF 50 sunscreens about 98%, and SPF 100 about 99%. The higher the SPF, the smaller the difference.21

As you can see, sunscreen should not be your only form of sun protection. Check out clothing with UV protection. Know that long-sleeved shirts, long pants, or long skirts are the most protective because they cover the most skin. Dark colors generally provide more protection than light colors. A tightly woven fabric protects better than looser weaves. Dry fabric is generally more protective than wet fabric.21 Read more from the American Cancer Society here.

If you have kids, you’ll want them to reapply their sunscreen during the school day, especially if they spend a lot of time outside. There are state laws in place to help and the Centers for Disease Control and Prevention has a handy Sun Safety tool that tells you which states have sunscreen laws. You can test your sunscreen knowledge here.

Genetics is focused on inherited disorders or inherited risks for developing cancer. Cancer is a group of genetic diseases due to changes in the DNA of the genome of cells in our bodies that lead them to grow uncontrollably.22,23 These changes, or abnormalities, can be DNA mutations, rearrangements, deletions, amplifications, or the addition or removal of chemical marks. Often, a combination of several changes works together to cause cancer.23

Genomics is the study of all of a person’s genes (the genome), including interactions of those genes with each other and a person’s environment.13,26 It is transforming how we study, diagnose, and treat cancer.22 The goal of genomics is to understand how combinations of genetic features change disease behavior as well as to understand genes and their functions. Genome-based medicine is also called personalized medicine and is designed to make treatment of disease as individualized as the disease itself is in each person.

Cancer genomics is relatively new and is helping to usher in an era of new cancer information that can help us better understand the molecular basis of cancer growth, metastasis, and drug resistance.23 To learn more, visit the National Cancer Institute’s Cancer Genomics Overview.

Cancer spreads in 3 ways. Through tissue, the lymph system, and the blood. With tissue, it spreads from where it started into nearby areas. Through the lymph system, it spreads by traveling through the lymph vessels to other parts of the body. Through blood, it spreads by traveling through blood vessels to other parts of the body.13

Familial atypical multiple mole melanoma syndrome is when you have hereditary risk factors as well as many atypical moles. This increases your risk of developing melanoma.11

The National Cancer Institute’s video reference explains these terms and shows how they report them through SEER (the Surveillance, Epidemiology, and End Results Program).

A measurement in millimeters that is taken from the surface of the skin to the deepest part of the melanoma. This is helps make up the T in the American Joint Committee on Cancer’s TNM classification system, along with tumor thickness and tumor ulceration.

Melanomas that are local or localized, meaning they have not spread, are considered early stage. These are Stage 0 and Stage I melanoma.30

Melanomas that are localized but are larger tumors. These may have ulcerations, which means they are at high risk for spreading (metastasizing). Stage II intermediate, high-risk melanomas are deeper than 1 mm think and may or may be ulcerated. No spread has been identified but the risk is high.30

Melanomas that have spread from the primary tumor, or original tumor site. These include Stage III and Stage IV melanomas.30

Mohs surgery is the short name for Mohs Micrographic Surgery. The advantage of Mohs surgery is that surgeons can tell if the tumor is completely removed before stitching the wound. This protects healthy tissue and leaves smaller scars. It is more often performed for noninvasive or early-stage melanoma than advanced melanoma.

Mohs surgery is sometimes used less for skin melanoma in situ because melanoma is far more aggressive (read likely to deepen and spread) than other types of skin cancer. Some doctors may fear missing microscopic melanoma cells that could end up spreading.

Also, the edges of non-melanoma skin cancers are easier to see under the microscope than melanoma cells, especially atypical melanoma cells. Recently, the addition of special stains, called immunohistology stains, which stick to the cells that develop melanoma has made the melanoma cells more prominent under the microscope. However, this technique requires special training that can limit its use.25