Melanoma: Stages

Approved by the Cancer.Net Editorial Board, 08/2020




Factors used for staging melanoma

To determine the stage of a melanoma, the lesion and some surrounding healthy tissue need 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 Diagnosis to help determine the disease’s stage.

Doctors also use results from diagnostic tests to answer these questions about the stage of melanoma:

  • How thick or deep is the original melanoma, often called the primary melanoma or primary tumor?

  • Where is the melanoma 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. The stages of melanoma include: 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.

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 relatively thin. Stage I is divided into 2 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 higher chance of spreading. Stage II is divided into 3 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 locally or through the lymphatic system 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, satellite metastasis, or microsatellite disease. 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 divided into 4 subgroups—A, B, C, or D—depending on the size and number of lymph nodes involved with melanoma, whether the primary tumor has satellite or in-transit lesions, and if it appears ulcerated under a microscope.


  • M1a: The cancer has only spread to distant skin and/or soft-tissue sites.

  • M1b: The cancer has spread to the lung.

  • M1c: The cancer has spread to any other location that does not involve the central nervous system.

  • M1d: The cancer has spread to the central nervous system, including the brain, spinal cord, and/or cerebrospinal fluid, or lining of the brain and/or spinal cord.

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.

