STAGING SQUAMOUS CELL SKIN CANCER:
A PRACTICAL DESCRIPTION

One of the first steps in determining your treatment plan is establishing the stage of your cancer. Unfortunately, there is no universally accepted staging system for squamous cell skin cancer (for more on the debate over staging systems, see SCIENCE SIDEBAR). Here we present a description of squamous cell skin cancer staging that is helpful for treatment planning. It is based on risk features and the designation of disease that is local and confined vs disease that has advanced (locally, to the lymph nodes, or beyond).

Local Squamous Cell Skin Cancer, Low-Risk Features

Local squamous cell skin cancer is generally characterized by smaller tumors with no high-risk features. It has a very low likelihood of advancing locally, becoming metastatic, or recurring. A typical situation would be a squamous cell skin cancer with no high-risk features on the trunk or extremities.

Low-risk cSCC — This image shows an in situ or Bowen’s disease tumor, where the tumor has not penetrated past the epidermis.

regular cSCC — This image shows a low-risk squamous cell skin cancer that has penetrated a little further (into the dermis) than the in situ tumor. However, it still does not have any high-risk features.

Local Squamous Cell Skin Cancer, High-Risk Features

These are tumors that are still localized but have some high-risk features. They are at high risk for coming back locally (recurrence), becoming locally advanced, or spreading (metastasis).

high-risk cSCC — This tumor extends further down into the dermis and involves the blood vessels, which is a high-risk feature.

Advanced Disease

The remaining cases can be described as advanced disease, which is the most challenging form of squamous cell skin cancer. Advanced disease includes tumors that have advanced locally (and can’t be managed with surgery), to the lymph nodes, or to sites far away in the body. The majority of people who die from squamous cell skin cancer initially present with advanced disease that is either locally advanced or regional (as discussed below).

Locally Advanced Squamous Cell Skin Cancer

We can think of a locally advanced squamous cell skin cancer as a subset of local squamous cell skin cancer with high-risk features. These are tumors that have already penetrated deep below the skin. Perhaps it’s helpful to think of the squamous cell skin cancer as a tree—a locally advanced case would be one where the roots get so big they lift up the sidewalk around the tree or reach so far down they wrap around sewer pipes and other underground structures, causing extensive damage. It is characterized by:

advanced cSCC — This tumor has invaded into the fascia (the connective tissue covering the muscle that is below the subcutaneous fat).

Tumor size is greater than or equal to 4 cm (approximately 1.5 inches)
The tumor is invasive, which means it
- Attacks the nerves or tissue around the bone
- Causes minor erosion (breaking) of bone
- Invades tissue beyond the subcutaneous fat
- Can progress to gross invasion of the “cortical bone” (deeper bone) or bone marrow

Science Sidebar

Staging Squamous Cell Skin Cancer: Many Paths to Risk Assessment

Why are there multiple staging systems for squamous cell skin cancer? In oncology, the most widely used (and recognized staging system) is the American Joint Committee on Cancer (AJCC) system. You may have heard about cancers being staged Stage I, II, III, or IV based on this system, which considers the following factors:

Size of the tumor (T) and if it has grown deeper into nearby structures or tissues, such as a bone
Presence/degree of spread (metastasis) to nearby lymph nodes (N)
Presence of spread (metastasized) to distant parts of the body (M)

Even though these factors are included in predicting the outcomes from squamous cell skin cancer, there are many risk factors that are considered, as outlined in the previous section Risk Assessment. You may hear mention of any of the following staging systems, all of which weigh the high-risk features differently:

AJCC 8th Edition Staging System (TNM plus other risk factors)
Brigham and Women’s Hospital Staging System (best for local disease, does not address N/M groupings)
National Comprehensive Cancer Network (NCCN) staging system (stratification)
Breuninger System (tumor size and histologic thickness)

The American Academy of Dermatology (AAD) recommends following the NCCN guidelines for practical guidance on how to treat squamous cell skin cancer, but it suggests that clinicians use the Brigham and Women’s Hospital Staging system to gain the most accurate prognosis for patients with localized squamous cell skin cancer.

What are the challenges of locally advanced squamous cell skin cancer?

There is the risk of invasion of deeper layers of the skin and spread to other parts of the body. If squamous cell skin cancer grows in and around the nerves, it can cause pain, numbness, or muscle weakness
Advanced squamous cell skin cancer can be difficult to treat. It might require several surgeries and can be disfiguring, requiring reconstructive surgery to repair the skin/other structures
As mentioned previously, patients with locally advanced disease are at increased risk of death from squamous cell skin cancer as compared with patients in whom the tumor is more confined locally

When squamous cell skin cancer spreads

Approximately four percent of squamous cell skin cancers will metastasize (spread) to the regional lymph nodes or to distant sites (other parts of the body). Patients who are immunosuppressed may have a two- to three-fold higher risk of metastasis, which means the risk for metastasis can be as high as 12 percent.

Regional Squamous Cell Skin Cancer (Nodal Disease)

Regional disease is characterized by cancer that has spread to nearby lymph nodes. Lymph nodes are small, seed-shaped structures that contain clusters of immune cells. Their function is to filter the lymphatic fluid, which helps to clear waste material from the tissues and deliver white blood cells to fight infections. Lymph nodes are found throughout the body, notably in the neck, armpit, and groin. Cancer cells typically spread from the primary tumor to the nearest lymph node before traveling to other parts of the body.

How is regional disease diagnosed?

If the lymph node feels swollen or if lymph nodes are identified by imaging, then the doctor will take a sample from the lymph node for testing by

fine needle aspiration, wherein a hollow thin needle is attached to a syringe to take out fluid/small amounts of tissue to examine
core needle biopsy, which uses a larger needle with a larger hollow center (bore). This involves getting a small section of tissue, which will give you more information

lymph nodes 1 — Cancer involving the lymph nodes. The diagram shows the primary tumor as well as the affected lymph nodes.

lymph nodes 2 — Skin cancer on the scalp that has spread through the lymphatics to a lymph node on the head.

Yellow sunburst shows the site of the primary tumor on the neck and spread to the lung, liver, and bone.

Distant Metastatic Squamous Cell Skin Cancer

This term classifies disease that has spread to other sites in the body—either to far away lymph nodes or the lungs, brain, or other organs, resulting in distant metastasis.

Your doctor can advise you if you need imaging to look for metastatic disease. S/he may order imaging if you have certain symptoms or abnormal laboratory tests. The additional imaging may include computed tomography (CT) or positron emission tomography/computed tomography (PET-CT). It’s important to note that most patients with squamous cell skin cancer will not need a CT scan, since the risk of distant metastatic disease is only 0.4%.

Key terms:

Computed tomography (CT) is a procedure that uses a computer linked to an x-ray machine to make a series of detailed pictures of areas inside the body. The pictures are taken from different angles and are used to create three-dimensional (3-D) views of tissues and organs. A dye may be injected into a vein or swallowed to help the tissues and organs show up more clearly. A CT scan may be used to help diagnose disease, plan treatment, or find out how well treatment is working. Also called CAT scan, computed tomography scan, computerized axial tomography scan, and computerized tomography.

PET-CT is a procedure that combines the pictures from a positron emission tomography (PET) scan and a computed tomography (CT) scan. The PET and CT scans are done at the same time with the same machine. The combined scans give more detailed pictures of areas inside the body than either scan gives by itself. A PET-CT scan may be used to help diagnose disease such as cancer, plan treatment, or find out how well treatment is working. Also called positron emission tomography-computed tomography scan.

Discussing Your Pathology Report

Here are some questions you can ask your heathcare provider about your pathology report and squamous cell skin cancer staging. It might be helpful to review the previous page High-Risk Features as well as this page so you are familiar with some of the concepts/terminology.

Talking With Your Doctor About Your Biopsy Results

Is this a particular type of squamous cell skin cancer?

Do I have any high-risk features? If so, how many and what are they?

What is my stage? What staging system are you using?

Is my squamous cell skin cancer localized or has it spread to my lymph nodes—or beyond?

Can I please have a copy of the pathology report?

What is my prognosis? How did you establish that?

Do I need a referral to any other specialists (such as a medical oncologist, radiation oncologist, or head-and-neck surgeon)?

STAGING SQUAMOUS CELL SKIN CANCER: A PRACTICAL DESCRIPTION