Melanoma: Stages

Approved by the Cancer.Net Editorial Board, 06/2014

ON THIS PAGE: You will learn about how doctors describe a melanoma’s growth or spread. This is called the stage. To see other pages, use the menu on the side of your screen.

Staging is a way of describing where the cancer is located, if or where it has spread, and whether it is affecting other parts of the body. Doctors use diagnostic tests to find out the cancer's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctors decide what type of treatment is best and can help predict a patient's prognosis, which is the chance of recovery. There are different stage descriptions for different types of cancer.

To determine the stage of a melanoma, the lesion and some surrounding healthy tissue needs to be surgically removed and analyzed using a microscope. Doctors use the melanoma’s thickness, measured in millimeters (mm), and other characteristics to help determine the disease’s stage. These factors are explained in the Diagnosis section.

In addition, doctors use the following factors to determine the stage of melanoma:

  • How large is the original melanoma, often called the primary melanoma or primary tumor, and where is it located?
  • Has the melanoma spread to the lymph nodes?
  • Has the melanoma metastasized to other parts of the body?

The results are combined to determine the stage of melanoma for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatment plan and understand a patient's prognosis when diagnosed.

Here are more details about each stage of melanoma.

Stage 0: This refers to melanoma in situ, which means melanoma cells are found only in the outer layer of skin, called the epidermis. This stage of melanoma has virtually no metastatic potential, which means it is very unlikely that it will spread to other parts of the body.

Stage I: The primary melanoma is still only in the skin and is very thin. Stage I is divided into two subgroups, IA or IB, depending on the thickness of the melanoma and whether a pathologist sees ulceration under a microscope.

Stage II: Stage II melanoma is thicker than stage I melanoma, extending through the epidermis and further into the dermis, the dense inner layer of the skin. It has a slightly higher chance of spreading. Stage II is divided into three subgroups—A, B, or C—depending on how thick the melanoma is and whether or not there is ulceration.

Stage III: This stage describes melanoma that has spread through the lymphatic system either to a regional lymph node located near where the cancer started or to a skin site on the way to a lymph node, called “in-transit metastasis.” The lymphatic system is part of the immune system and drains fluid from body tissues through a series of tubes or vessels. Stage III is also divided into subgroups—A, B, or C—depending on the size and number of lymph nodes involved with melanoma and whether the primary tumor appears ulcerated under a microscope. 

Stage IV: This stage describes melanoma that has spread through the bloodstream to other parts of the body, such as distant locations on the skin or soft tissue, distant lymph nodes, or other organs like the lung, liver, brain, bone, or gastrointestinal tract. Stage IV is further divided into M1a, which means the cancer has only spread to distant skin and/or soft tissue sites; M1b, which involves metastasis to the lung; and M1c, which describes distant metastasis at any other location or an elevated serum lactate dehydrogenase (LDH) blood test.

Recurrent: Recurrent melanoma is melanoma that has come back after treatment. If there is a recurrence, the cancer may need to be staged again (re-staging).

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Seventh Edition (2010) published by Springer-Verlag New York,

Information about the cancer’s stage will help the doctor recommend a treatment plan. The next section helps explain the treatment options for this type of cancer. Use the menu on the side of your screen to select Treatment Options, or you can select another section, to continue reading this guide.