How is Squamous Cell Skin Cancer Staged?
Unlike many types of cancers with a numerical staging system, squamous cell skin cancer (SCSC) follows a unique categorization based on the risk assessment of the primary tumor. This unique staging system puts most SCSCs into one of three groups: Low-Risk, High-Risk, or Very High-Risk. Treatment options are then based on each category to prevent recurrence and spread beyond the initial tumor. Tumor location and size are the basis for this categorization.
Very rarely are SCSC tumors metastatic and have spread from the initial site. Some tumor cells may be detected in regional lymph nodes. Tumors that spread far beyond the primary site require more complicated treatment procedures. The highest risk factor you have present will be used to assign your cancer stage.
Local, Low-Risk Squamous Cell Skin Cancer
SCSCs that are categorized as low-risk are also called primary and are not recurrent tumors. They are more likely to develop on the trunk and extremities and are less than two centimeters (cm) in size and two millimeters (mm) in depth. These small tumors are unlikely to return or become metastatic. They have well-defined edges and are not invasive.
Local, High-Risk Squamous Cell Skin Cancer
The group of SCSCs categorized as high-risk have an elevated risk of local recurrence. They are more likely to metastasize than the low-risk group. These tumors are between two cm and four cm in size and are associated with a poorer disease-specific survival. High-risk SCSCs have poorly defined edges and grow rapidly.
High-risk SCSCs will often appear on the head and neck area, including the ears and lips. Besides the head and neck, SCSCs that develop on the hands and feet, or the pretibial (shin), and anogenital (anus and genital) areas are also at greater risk of local recurrence and nodal metastasis, independent of size. Any tumors that have returned are defined as high risk. Tumors that have invaded deeply into the skin dermis or subcutaneous fat at a depth of two to six mm are also considered high risk.
High-risk categorization may also apply to people with immunosuppression from organ transplantation, HIV, lymphoma, or chronic lymphocytic leukemia (CLL). If the SCSC occurs on a site of chronic inflammation or prior radiation therapy, it is considered high-risk. Neurological symptoms could be apparent in people with high-risk SCSC.
Local, Very High-Risk Squamous Cell Skin Cancer
The very high-risk group has considerable risks of local SCSC recurrence and metastasis, more so than the low- and high-risk groups. Any SCSC tumor with a diameter of greater than four cm in size is considered at very high-risk for recurrence, regardless of its location. Tumors that are greater than five cm in size have a significant association with cancer detected in the lymph nodes. Very high-risk has invaded deeply, greater than six mm beyond the subcutaneous fat.
The very high-risk categorization is marked by involvement with the lymphatic or vascular systems, not merely localization at the original skin site. This means that cancer cells are in your lymph nodes, the small filters of the immune system located throughout your body, or in your blood system. If the SCSC tumors have traveled away from your skin, it is referred to as “nodal disease,” the severity of which varies based on the size, number, and location of the lymph nodes with tumor cells. Your health care team will determine the extent of the spread through imaging and biopsies.
Regional or Metastatic Squamous Cell Skin Cancer
In rare cases, the SCSC can develop beyond the local, primary site on the skin. It may have spread in the area (regional) to lymph nodes or distant sites (metastasis). Among SCSC tumors less than or equal to two millimeters (mm) in thickness, the rate of metastasis is usually 0%. For SCSC tumors greater than two mm and up to six mm in thickness, the rate of metastasis is about 4%, and for tumors thicker than six mm, the rate is about 16%. Clinical examination of biopsies and images inside the body will confirm the extent of disease spread.
Understanding CSCC Risk Levels
Not all cutaneous squamous cell carcinomas (CSCC) carry the same level of risk. Some tumors remain localized and are unlikely to return or spread after treatment, while others have characteristics that may make them more likely to recur, grow into surrounding tissue or spread to other areas of the body.
Healthcare providers evaluate several characteristics of a CSCC when determining its level of risk. These can include the tumor’s size, depth and location, as well as how the cancer is growing and whether certain additional risk factors are present.
In this video, we explain the differences between local low-risk, local high-risk and very high-risk CSCC. We also look at factors that may contribute to higher-risk disease, including a weakened immune system, previous radiation therapy, chronic inflammation and repeated injury to the skin.
For some people with very high-risk CSCC, cancer cells may spread to nearby lymph nodes or, less commonly, to other parts of the body. Understanding the characteristics and extent of the cancer helps the healthcare team determine an appropriate treatment approach and plan for follow-up care.
In This Video
You’ll learn:
• How CSCC is categorized by risk
• Characteristics of local low-risk CSCC
• Characteristics of local high-risk and very high-risk CSCC
• Factors that may increase the risk of recurrence or spread
• How nearby lymph nodes may become involved
• Why understanding the risk and extent of CSCC is important when planning treatment