Stages and Risk Groups of Squamous Cell Carcinoma of the Skin

Staging is the process of figuring out if cancer has spread, and if so, how far. The stage of a cancer describes how much cancer is in the body. Staging is important for most types of cancer to help determine the best treatment options.

Squamous cell carcinoma (SCC) of the skin, also known as squamous cell skin cancer, doesn’t usually spread beyond where it starts, so it often doesn’t need to be staged.

Other factors aside from the stage can help give an idea of how serious the cancer is likely to be. These are often used to divide SCC into risk groups.

Do all squamous cell carcinomas need to be staged?

Staging isn’t always needed for SCC because these skin cancers are often cured before they spread to other parts of the body.

Staging is more likely to be important if an SCC is at higher risk of returning after treatment or of spreading to other parts of the body. This is determined by factors that are described below, in “Risk groups for squamous cell skin cancer.”

When staging is done, it is based on the results of physical exams, biopsies, and any imaging tests that are done.

How is the stage determined?

The system most often used to stage squamous cell skin cancers is the American Joint Committee on Cancer (AJCC) TNM system.

This staging system applies only to squamous cell skin cancers of the head and neck area – the lips, ears, face, scalp, and neck. These cancers tend to have a higher risk of recurring (coming back) or spreading compared with SCCs in other parts of the body.

The stage is based on 3 key pieces of information:

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

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 the T, N, and M categories have been determined, this information is combined 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 through IV. As a rule, the lower the number, the less the cancer has spread.

Although the AJCC system is most common, other staging systems have also been developed. For example, the Brigham and Women’s Hospital (BWH) Tumor Staging system uses different risk factors to determine the T categories for squamous cell skin cancers of the head and neck area.

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.

To learn more about how cancers are staged, see Cancer Staging.

Risk groups for squamous cell skin cancer

The National Comprehensive Cancer Network (NCCN) develops treatment guidelines for cancer care. The NCCN uses certain factors to divide squamous cell skin cancers into risk groups, which can be used to help determine the best treatment options.

SCCs are divided into 3 risk groups, based on how likely they are to spread or to come back after treatment.

Very high-risk SCCs

SCCs in the very high-risk group have an increased risk of both coming back after treatment and of spreading to another part of the body. They have at least one of the following features:

• The tumor is larger than 4 cm across.
• The cancer cells look poorly differentiated (very abnormal) under a microscope.
• The tumor is more than 6 mm deep, or it has grown beyond the fat layer below the skin (subcutaneous fat).
• Cancer cells have invaded a nerve deeper than the dermis layer of the skin.
• Cancer cells have invaded a blood vessel or lymph vessel in or near the tumor.

High-risk SCCs

SCCs in the high-risk group have an increased risk of coming back after treatment. These cancers don’t have any of the very high-risk features above, but they have at least one of the following features:

• The tumor is on the chest, back, arm, or leg (other than the front of the lower leg), AND it’s at least 2 cm but no more than 4 cm across.
• The tumor is on any other part of the body, such as the head, neck, hands, feet, front of the lower leg, or genital area, regardless of size.
• The borders of the tumor aren’t well defined.
• The tumor is a recurrence, as opposed to a new tumor.
• The tumor is in a place that was previously treated with radiation, or it’s in a place where there’s been chronic (long-term) inflammation.
• The tumor shows signs of growing quickly.
• The tumor is causing neurologic symptoms, such as pain or itching.
• The cancer has adenosquamous or sarcomatoid areas when seen under a microscope.
• The tumor is 2 to 6 mm deep but has not grown beyond the fat layer below the skin (subcutaneous fat).
• Cancer cells have invaded small nerves in or near the tumor, known as perineural invasion.
• The person with SCC has a weakened immune system.

Low-risk SCCs

SCCs that don’t have any of the features in either group above are in the low-risk group.

To learn more about how these risk groups might affect your treatment options, see Treating Squamous Cell Carcinoma of the Skin.