Merkel Cell Carcinoma (MCC) Stages

After someone is diagnosed with Merkel cell cancer (MCC), 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. Doctors also use a cancer's stage when talking about survival statistics.

The earliest stage Merkel cell cancers are called stage 0 (or carcinoma in situ), and then range from stages I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, like stage IV, means cancer has spread more. And within a stage, an earlier letter means a lower stage. Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

How is the stage determined?

The staging system most often used for Merkel cell cancer is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

• The extent (size) of the tumor (T): How large is the cancer? Has it grown into nearby structures or organs?
• Spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes ?
• Spread (metastasis) to distant sites (M): Has the cancer spread to distant lymph nodes or distant organs such as the lungs and skin?

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 get an overall stage. For more on this, see Cancer Staging.

The 2 main types of staging for MCC are.

• The clinical stage is based on the results of physical exams, biopsies, and any imaging tests that have been done (as described in Tests for Merkel Cell Carcinoma). The clinical stage can be used to help plan treatment.
• After the skin biopsy to confirm the diagnosis, if surgery is done (to remove more of the area around the skin tumor, as well as to check nearby lymph nodes for cancer), the pathological stage (also called the surgical stage) can be determined.

The staging system in the table below is the pathological stage, which is the staging system most often used for Merkel cell carcinoma. But if surgery can't be done right away (or at all), the cancer will be given a clinical stage instead.

Clinical staging for Merkel cell cancer follows a separate staging system that's not covered in the table below. If your cancer has been clinically staged, ask your doctor for information about your specific stage.  

Staging for Merkel cell carcinoma can be complex, so ask your doctor to explain it to you in a way you understand.

 

 

AJCC Stage	Stage grouping	Stage description*
0	Tis N0 M0	The main tumor is still only in the top layer of skin (Tis). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). This stage is also known as carcinoma in situ (Tis).
I	T1 N0 M0	The main tumor is no more than 2 centimeters (cm) across (about 4/5 inch). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IIA	T2 or T3 N0 M0	The main tumor is more than 2 but less than 5 cm (about 2 inches) across (T2) OR the tumor is more than 5 cm across (T3). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IIB	T4 N0 M0	The main tumor has grown into nearby tissues such as muscles, bones, or cartilage (T4). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IIIA	T1, T2, T3, or T4 N1a(sn) or N1a M0	The main tumor can be any size or may have grown into nearby tissues (T1, T2, T3, or T4) AND the cancer has spread to nearby lymph nodes, but this was found during a lymph node biopsy or surgery and was not seen on exams or imaging tests (N1a[sn] or N1a). The cancer has not spread to distant parts of the body (M0).
	OR
	T0 N1b M0	There's no sign of a main tumor (T0) AND the cancer has spread to nearby lymph nodes, which was seen on exams or imaging tests and then confirmed by biopsy or surgery (N1b). The cancer has not spread to distant parts of the body (M0).
IIIB	T1, T2, T3, or T4 N1b, N2 or N3 M0	The main tumor can be any size or may have grown into nearby tissues (T1, T2, T3, or T4) AND any of the following: The cancer has spread to nearby lymph nodes, which was seen on exams or imaging tests and then confirmed by biopsy or surgery (N1b). The cancer has spread toward a nearby lymph node area without reaching the lymph nodes (N2). This is called in transit metastasis. The cancer has spread toward a nearby lymph node area (called in transit metastasis) and has reached the lymph nodes (N3). The cancer has not spread to distant parts of the body (M0).
IV	T0, T1, T2, T3 or T4 Any N M1	The main tumor can be any size or may have grown into nearby tissues (T0, T1, T2, T3, or T4) AND the cancer might or might not have spread to nearby lymph nodes (Any N). The cancer has spread to distant lymph nodes or organs, such as the lungs or distant areas of skin (M1).

* The following categories are not listed on the table above:

• TX: Main tumor cannot be assessed due to lack of information.
• T0: No evidence of a primary tumor.
• NX: Regional lymph nodes cannot be assessed due to lack of information.