Merkel cell carcinoma is most frequently diagnosed after a patient notices skin changes and visits the doctor, where a biopsy and other tests (including imaging tests and blood tests) are conducted.

Since MCC often quickly spreads to nearby lymph nodes, the nodes are checked once a diagnosis is confirmed. A sentinel lymph node biopsy (SLNB) is a common way to determine whether the disease has spread.

Find out more about what happens during a sentinel lymph node biopsy.

After testing is finished, your medical team will try to pinpoint how far the disease has progressed. This process is known as staging. Staging is a way to understand how much the cancer has grown and how far it has spread. This helps determine how to best treat it, and the risk of it coming back.

The TNM system is frequently used to stage MCC. It’s a classification based on three factors:

• T represents the size of the original tumor, its growth rate and other factors.

• N indicates whether the cancer has spread to the local lymph nodes and to what extent.

• M stands for the spread or metastasis to distant lymph nodes and organs.

Once the patient’s TNM categories have been established, the overall stage number is assigned. As a rule, the lower the stage number, the less the disease has progressed.