Find out what Clark and Breslow staging means for melanoma skin cancer.
The stage of a melanoma describes how deeply it has grown into the skin, and whether it has spread.
Doctors use 2 scales to describe how deeply the melanoma has gone into the skin. These are called the:
- Clark scale
- Breslow scale
These scales are different to the number staging system that doctors also use. The Clark and Breslow scales only look at the depth of melanoma cells in the skin. The number stages look at the melanoma depth, and also whether the melanoma has spread to lymph nodes or another part of the body.
The Clark scale is a way of measuring how deeply the melanoma has grown into the skin and which levels of the skin are affected. You can see the main layers of the skin in this diagram.
The Clark scale has 5 levels:
Level 1 is also called melanoma in situ – the melanoma cells are only in the outer layer of the skin (the epidermis)
Level 2 means there are melanoma cells in the layer directly under the epidermis (the papillary dermis)
Level 3 means the melanoma cells are throughout the papillary dermis and touching on the next layer down (the reticular dermis)
Level 4 means the melanoma has spread into the reticular or deep dermis
Level 5 means the melanoma has grown into the layer of fat under the skin (subcutaneous fat)
For the Breslow scale, the pathologist measures the thickness of your melanoma with a small ruler, called a micrometer. A pathologist is the doctor who examines the melanoma cells in the laboratory.
Doctors use a scale called the primary tumour thickness scale, or the Breslow thickness. It measures in millimetres (mm) how far your melanoma cells have reached down through the skin from the surface.
Doctors use the Breslow thickness in the TNM staging system for melanoma.