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.
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.
Factors used for staging melanoma
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 the other characteristics described in the Diagnosis  section to help determine the disease’s stage.
Doctors also use results from diagnostic tests to answer these questions about 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? If so, where and how many?
Has the melanoma metastasized to other parts of the body? If so, where and how much?
The results are combined to determine the stage of melanoma for each person. There are 5 stages of melanoma: stage 0 (zero) and stages I through IV (1 through 4). The stage provides a common way of describing the cancer, so doctors can work together to create the best treatment plan and understand a patient's prognosis.
Here are more details about each stage of melanoma.
Melanoma stage grouping
Stage 0: This refers to melanoma in situ, which means melanoma cells are found only in the outer layer of skin or epidermis. This stage of melanoma is very unlikely to 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, the mitotic rate, 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 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 the melanoma does return, there will be a round of tests to learn about the extent of the recurrence. These tests and scans may be similar to those done at the time of the original diagnosis .
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, published by Springer-Verlag New York, www.cancerstaging.net .
Information about the cancer’s stage will help the doctor recommend a specific treatment plan. The next section in this guide is Treatment Options . Or, use the menu to choose another section to continue reading this guide.