Stages of Melanoma Skin Cancer

Medically Reviewed by Stephanie S. Gardner, MD on September 18, 2023
3 min read

If you have melanoma skin cancer, your doctor will say it’s in one of five stages as a way to describe how far along it is. These are numbers, going from 0 through Roman numerals I to IV. Stage 0 melanoma has developed the least. Stage IV has gone the farthest.

Your stage will help your doctor decide how to treat the cancer. Most doctors use the TNM system to figure out the stage. It’s based on the following questions:

  • T(umor): How deep into your skin has the tumor gone? Has it broken down the skin over it? (That could show that your skin is casting off dead cells and may mean that a tumor is growing fast. You might hear your doctor call this ulceration.)
  • Lymph N(odes): Has the cancer spread to the tiny bean-shaped lymph nodes that are scattered throughout your body? (They hold white blood cells that help you fight off disease.)
  • M(etastasis): Has the cancer spread to your lungs, brain, or other organs? If so, your doctor might say the cancer has metastasized.

This means the cancer is in the very top layers of skin and hasn’t spread to other areas. Your doctor might call this melanoma in situ.

This means you have a cancerous tumor that’s less than 2 millimeters thick. (The point of a sharp pencil is about 1 millimeter wide, and the eraser on a new pencil is about 5 millimeters wide.)

Doctors divide stage I into two levels:

Stage IA -- The tumor is no more than 1 millimeter thick. It might have broken down the skin on top of it.

Stage IB -- The tumor is 1 to 2 millimeters thick, but it hasn’t broken down the skin on top of it.

If you have stage I melanoma, it hasn’t spread beyond the original tumor.

In this stage, the cancerous tumor is larger.

Stage IIA -- The cancer is either:

  • 1 to 2 millimeters thick and has broken down the skin on top of it, OR
  • 2 to 4 millimeters thick but hasn’t broken down the skin on top of it.

Stage IIB -- The cancerous tumor is either:

  • 2 to 4 millimeters thick and has broken down the skin, OR
  • More than 4 millimeters thick but hasn’t broken down the skin.

Stage IIC -- The tumor is more than 4 millimeters thick, and it has broken down the skin on top of it.

In this stage, the cancer has started to spread. It’s in:

  • More than one lymph node, OR
  • Tiny new tumors (called satellite or microsatellite tumors) near the original cancer, OR
  • The cells between the original cancer and the nearest lymph node (called in-transit tumor spread).

Doctors divide stage III into four detailed categories (A, B, C, and D) based on things like size and how far it’s spread.

This means the cancer has spread to your lungs, brain, bones, or other parts of your body. Melanoma also might show up on your skin in parts of your body far from the original tumor.

Your doctor might talk about stage IV in smaller categories that start with an M. That stands for “metastasis,” the term doctors use when cancer spreads.

M1a -- The cancer is in your skin in a different part of your body from the original tumor.

M1b -- Cancer is in your lungs.

M1c -- Cancer is in some other part of your body, but not your central nervous system.

M1d -- Cancer is in your brain, spinal cord, or another part of your central nervous system.

Your medical team will help you get a handle on your treatment and how likely you are to get well. In general, the lower the stage, the better your odds.

But everyone is different. Your chances of recovery can depend on many things, like your overall health and how well your treatment works for you.