Skin cancers are by far the most common type of cancer. According to the National Cancer Institute, between 40% and 50% of Americans who live to be 65 or older will have either basal cell carcinoma or squamous cell carcinoma (the two main types of skin cancer) at least once.
Another interesting fact? Each year, more new cases of skin cancer are diagnosed than cancers of the breast, prostate, lung and colon combined.
Because of the prevalence of skin cancer, it’s important to understand the different types and stages of skin cancer.
Non-Melanomas and Melanomas
There are three main types of skin cancer:
Basal cells are formed beneath the skin’s surface and divide quickly to form new cells. These cells move up toward the outer layer of skin and eventually flatten and become squamous cells.
BCC is the most frequently occurring skin cancer, with more than 4 million cases diagnosed in the U.S. each year, according to the Skin Cancer Foundation.
Basal cell carcinomas grow relatively slowly compared to other types of cancer. Therefore, there’s often no need to stage this type of skin cancer.
Squamous cells make the outer layer of skin. These cells constantly shed as new squamous cells are formed. Squamous cell carcinoma is the second-most common type of skin cancer. According to the Skin Cancer Foundation, about 1 million new cases of squamous cell carcinoma are diagnosed each year.
Squamous cell carcinomas grow slightly faster than basal cell cancers, but not much. It can be important to stage squamous cell carcinomas, especially if the patient has a weakened immune system.
Melanoma begins in skin cells called melanocytes. Melanocytes produce a pigment called melanin, which gives skin its tan or brown color. When most of us are exposed to the sun, our melanocytes produce more melanin, causing our skin to become red or tan.
About 87,000 new cases of invasive melanoma will be diagnosed in 2017, according to the Skin Cancer Foundation. And while melanoma makes up only about 4% of skin cancer cases, it’s the most aggressive form. In fact, it is the leading cause of death for women between the ages of 25 and 30.
Because melanomas are more aggressive, staging is crucial.
Stages of Cancer
Cancer staging is a process that helps define how much cancer is in the body and where it is located. The American Joint Committee on Cancer (AJCC) developed one of the most widely used cancer-staging references in the U.S.
To stage cancers, physicians consider:
- The location of the original tumor
- The tumor’s size and how extensive it is
- Whether any lymph nodes near the tumor are involved
- Metastasis (whether the cancer cells have spread to distant areas of the body)
“When a patient presents with an area of concern, we have a number of tools that help us determine if the area is indeed cancerous and, if so, the stage of skin cancer,” says Dr. Russell Peckham of U.S. Dermatology Partners Cedar Park.
“We almost always start with a family medical history to see if cancer is prevalent among the patient’s family. We also want to know if the patient has had a lot of sun exposure throughout his or her life,” Dr. Peckham adds. “People who grew up water-skiing on lakes or sunbathing on the beach are going to have a higher risk for skin cancers.”
Beyond the medical history and physical exam, there are several different types of skin biopsies that can be used to help determine the stage of skin cancer. A biopsy is when the area, or part of it, is removed and then sent to a lab to be viewed under a microscope.
Patients receive numbing medicine prior to the biopsy to help keep pain to a minimum.
How Skin Cancers are Staged
The Union for International Cancer Control and the AJCC developed a framework for staging cancer, called the TNM staging system.
T = Tumor (whether the tumor is in one spot, or if it has become invasive in nearby areas; also, the size of the tumor)
N = Node (whether there is lymph node involvement)
M = Metastases (whether the cancer has spread from its original point to a distant part of the body)
The “T,” “N” and “M” categories each have sub-classifications within them. Once the TNM classifications have been determined, a total score of 0 to IV is given.
Stages of Skin Cancer: Basal Cell and Squamous Cell Carcinoma
- Stage 0. The cancerous cells are confined to the outer layer of skin (epidermis) and have not spread deeper into the dermis. This stage may also be called in situ, which is Latin for in place.
- Stage I. The cancer is no larger than 2 centimeters and measures approximately 4/5 of an inch across. It has not spread to lymph nodes.
- Stage II. Here, the cancer is larger than 2 centimeters across, but it has not spread to organs or lymph nodes.
- Stage III. In stage III, cancer has spread into facial bones or one nearby lymph node, but not to other organs.
- Stage IV. Cancer can be of any size. It has metastasized (or spread) to one or more lymph nodes and may have spread to bones or other organs in the body.
Stages of Skin Cancer: Melanoma
- Stage 0. Also called melanoma in situ, the cancer is confined to the outer layer of skin.
- Stage I. The melanoma is up to 2 millimeters in thickness and may or may not be ulcerated. It has not spread to lymph nodes or metastasized.
- Stage II. The cancer is larger than 2 millimeters and is ulcerated. It has not spread to lymph nodes or metastasized to distant organs.
- Stage III. This stage is determined by the level of lymph node involvement and ulceration. It has not metastasized to other organs.
- Stage IV. In stage IV, the cancer has spread beyond the original site and nearby lymph nodes to more distant organs. Most commonly, melanoma spreads to the lungs, abdominal organs, brain, bone, and soft tissue.
While any diagnosis of cancer is scary, early detection is key. Know the signs of skin cancer and make an appointment to see a dermatologist if you have an area that’s concerning.
Looking to Visit a Dermatologist for Skin Cancer Treatment?
Keep in mind that there are also many treatment options for skin cancer, depending on the type you have. We have multiple locations throughout the country, so fill out our simple online form to get in touch with us. One of our local team members will reach out to you shortly to answer your questions or schedule an appointment for you to visit us soon.
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