Basal and Squamous Cell Skin Cancer Stages

After someone is diagnosed with cancer, doctors will try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it.

The stage is based on the results of the physical exam, the skin biopsy (and any other biopsies), and the results of imaging tests if they are done. These exams and tests are described in Tests for Basal and Squamous Cell Skin Cancers.

Determining the stage of basal cell skin cancers is rarely needed, because these cancers are almost always cured before they spread to other parts of the body.

Squamous cell skin cancers are more likely to spread (although this risk is still small), so determining the stage can be more important, particularly in people who are at higher risk. This includes people with weakened immune systems, such as those who have had organ transplants and people infected with HIV, the virus that causes AIDS. Most squamous cell skin cancers occur in the head and neck region and tend to have a higher risk of recurring (coming back) or spreading compared to those in other locations.

How is the stage determined?

The system most often used to stage basal and squamous cell skin cancers is the American Joint Commission on Cancer (AJCC) TNM system. The most recent version, effective as of 2018, applies only to squamous and basal cell skin cancers of the head and neck area (lip, ear, face, scalp and neck). The stage is based on 3 key pieces of information:

• The size of the tumor (T)  and if it has grown deeper into nearby structures or tissues, such as a bone
• If the cancer has spread to nearby lymph nodes (N)
• If the cancer has spread (metastasized) to distant parts of the body (M)

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.

Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. The earliest stage of skin cancer is stage 0 (also called carcinoma in situ, or CIS). The other stages range from I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more.

If your skin cancer is in the head and neck area, talk to your doctor about your specific stage. Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand. For more information, see Cancer Staging.

Other factors that can affect outlook and treatment options

The stage of a skin cancer can help give an idea of how serious the cancer is likely to be, including how likely it might be to return after treatment. But other factors are also important to consider. Some of these include:

• The location of the tumor
• How fast the tumor has been growing
• How well-defined the borders of the tumor are
• If the tumor has been causing symptoms, such as pain or itchiness
• How the cancer cells look under a microscope
• If the cancer cells have invaded small nerves or blood vessels in and around the tumor
• If the cancer is in a place that was previously treated with radiation
• If the person has a weakened immune system

Your doctor can explain if any of these factors might affect your treatment or outlook.