Cancer stages describe the size of the primary tumor and how far cancer has spread from where it started. There are different staging guidelines for different types of cancer.

Staging provides an overview of what to expect. Your doctor will use this information to come up with the best possible treatment plan for you.

In this article, we’ll take an in-depth look at how basal cell, squamous cell, and melanoma skin cancers are staged.

Cancer is a disease that starts in one small area of the body, like the skin. If it’s not treated early, it may spread to other parts of the body.

Doctors use staging information to understand:

  • how much cancer is in a person’s body
  • where the cancer is located
  • whether the cancer has spread beyond where it started
  • how to treat the cancer
  • what the outlook or prognosis is

Although cancer tends to be different for everyone, cancers with the same stage are typically treated the same way and often have similar outlooks.

Doctors use a tool known as the TNM classification system to stage different types of cancer. This cancer staging system involves the following three points of information:

  • T: tumor size and how deep it’s grown into the skin
  • N: lymph node involvement
  • M: metastasis or whether the cancer has spread

Skin cancers are staged from 0 to 4. As a general rule, the lower the staging number, the less the cancer has spread.

For instance, stage 0, or carcinoma in situ, means abnormal cells, which have the potential to become cancerous, are present. But these cells remain in the cells where they first formed. They haven’t grown into nearby tissue or spread to other areas.

Stage 4, on the other hand, is the most advanced. At this stage, the cancer has spread to other organs or parts of the body.

Staging usually isn’t needed for basal cell skin cancer. That’s because these cancers are often treated before they spread to other areas.

Squamous cell skin cancers have a higher probability of spreading, although the risk is still fairly low.

With these types of skin cancers, certain features can make the cancerous cells more likely to spread or return if it’s removed. These high risk features include:

  • a carcinoma (cancerous cells) thicker than 2 mm (millimeters)
  • invasion into the nerves in the skin
  • invasion into the lower layers of the skin
  • location on the lip or ear

Squamous cell and basal cell skin cancers are staged as follows:

  • Stage 0: The cancerous cells are only present in the upper layer of the skin (epidermis) and haven’t spread deeper into the skin.
  • Stage 1: The tumor is 2 cm (centimeters) or less, hasn’t spread to nearby lymph nodes, and has one or fewer high risk features.
  • Stage 2: The tumor is 2 to 4 cm, hasn’t spread to nearby lymph nodes, or the tumor is any size and has two or more high risk features.
  • Stage 3: The tumor is more than 4 cm, or it has spread to one of the following:
    • subcutaneous tissue, which is the deepest, innermost layer of skin that includes blood vessels, nerve endings, and hair follicles
    • bone, where it has caused minor damage
    • a nearby lymph node
  • Stage 4: The tumor can be any size and has spread to:
    • one or more lymph nodes, which are larger than 3 cm
    • bone or bone marrow
    • other organs in the body

If squamous cell or basal cell skin cancer is caught early, it’s very treatable. Different surgical techniques are most often used to remove the cancerous cells.

These surgical procedures are usually done in a doctor’s office or outpatient clinic under local anesthesia. This means you’ll be awake, and only the area around the skin cancer will be numbed. The type of surgical procedure that’s done will depend on:

  • the type of skin cancer
  • the size of the cancer
  • where the cancer is located

If the cancer has spread deeper into the skin or has a higher risk of spreading, other treatments may be needed after surgery, such as radiation or chemotherapy.

Some of the most common treatment options for basal cell or squamous cell skin cancers include the following:

  • Excision: With excision, your doctor will use a sharp razor or scalpel to remove the cancerous tissue and some of the healthy tissue around it. The tissue that’s removed will then be sent to a laboratory for analysis.
  • Electrosurgery: Also known as curettage and electrodesiccation, this procedure is best suited to skin cancer that’s on the uppermost surface of the skin. Your doctor will use a special instrument called a curette to remove the cancer. The skin is then burned with an electrode to destroy any remaining cancer. This procedure is usually repeated a couple of times during the same office visit to make sure all the cancer is removed.
  • Mohs surgery: With this procedure, your doctor uses a scalpel to carefully remove the abnormal skin in horizontal layers along with some of the surrounding tissue. The skin is examined under a microscope as soon as it’s removed. If cancer cells are found, another layer of skin is removed immediately until no more cancer cells are detected.
  • Cryosurgery: With cryosurgery, liquid nitrogen is used to freeze and destroy the cancerous tissue. This treatment is repeated several times during the same office visit to make sure all the cancerous tissue has been destroyed.

Although melanoma is less common than basal cell or squamous cell skin cancers, it’s more aggressive. This means that it’s more likely to spread to nearby tissues, lymph nodes, and other parts of the body, compared with nonmelanoma skin cancers.

Melanoma is staged as follows:

  • Stage 0: The cancerous cells are only present in the outermost layer of skin and haven’t invaded nearby tissue. At this noninvasive stage, the cancer can be removed by surgery alone.
  • Stage 1A: The tumor isn’t more than 1 mm thick. It may or may not be ulcerated (a break in the skin that allows the tissue below to show through).
  • Stage 1B: Tumor thickness is 1 to 2 mm, and there’s no ulceration.
  • Stage 2A: Tumor is 1 to 2 mm thick and ulcerated, or it’s 2 to 4 mm and not ulcerated.
  • Stage 2B: Tumor is 2 to 4 mm thick and ulcerated, or it’s more than 4 mm and not ulcerated.
  • Stage 2C: Tumor is more than 4 mm thick and ulcerated.
  • Stage 3A: Tumor thickness isn’t more than 1 mm and there’s ulceration, or it’s 1 to 2 mm and not ulcerated. Cancer is found in 1 to 3 sentinel lymph nodes.
  • Stage 3B: The tumor is up to 2 mm thick with ulceration, or 2 to 4mm without ulceration, plus cancer is present in one of these:
    • one to three lymph nodes
    • in small groups of tumor cells, called microsatellite tumors, right next to the primary tumor
    • in small groups of tumor cells within 2 cm of the primary tumor, called satellite tumors
    • in cells that have spread to nearby lymph vessels, known as in-transit metastases
  • Stage 3C: The tumor is up to 4 mm thick with ulceration, or 4 mm or larger without ulceration, plus cancer is present in one of these:
    • two to three lymph nodes
    • one or more nodes, plus there are microsatellite tumors, satellite tumors, or in-transit metastases
    • four or more nodes or any number of fused nodes
  • Stage 3D: Tumor thickness is over 4 mm and it’s ulcerated. Cancer cells are found in either of these locations:
    • four or more lymph nodes or any number of fused nodes
    • two or more nodes or any number of fused nodes, plus there are microsatellite tumors, satellite tumors, or in-transit metastases
  • Stage 4: Cancer has spread to distant parts of the body. This may include lymph nodes or organs such as the liver, lungs, bone, brain, or digestive tract.

For melanoma, treatment will largely depend on the stage and location of the cancerous growth. However, other factors may also determine what type of treatment is used.

  • Stage 0 and 1: If melanoma is detected early, surgical removal of the tumor and surrounding tissue is usually all that’s required. Routine skin screening is recommended to ensure that no new cancer develops.
  • Stage 2: The melanoma and surrounding tissue will be surgically removed. Your doctor may also recommend a sentinel lymph node biopsy to make sure the cancer hasn’t spread to nearby lymph nodes. If the lymph node biopsy detects cancer cells, your doctor may recommend surgical removal of the lymph nodes in that area. This is known as lymph node dissection.
  • Stage 3: The melanoma will be surgically removed along with a larger amount of surrounding tissue. Because the cancer has spread to the lymph nodes by this stage, treatment will also include lymph node dissection. After surgery, additional treatments will be recommended. They may include:
    • immunotherapy drugs that help boost your immune system’s response against cancer
    • targeted therapy drugs that block certain proteins, enzymes, and other substances that help cancer grow
    • radiation therapy that’s focused on the areas where the lymph nodes were removed
    • isolated chemotherapy, which involves infusing just the area where the cancer was located
  • Stage 4: Surgical removal of the tumor and lymph nodes is typically recommended. Because the cancer has spread to distant organs, additional treatment will likely include one or more of the following:

Skin cancer stages can tell you a lot about how far the disease has progressed. Your doctor will consider the specific type of skin cancer and the stage to determine the right treatment for you.

Early detection and treatment generally provide the best outlook. If you’re at high risk for skin cancer or notice something unusual on your skin, schedule a skin cancer screening as soon as possible.