If the biopsy shows that you have skin cancer, your doctor needs to learn the stage (extent) of the disease to help you choose the best treatment.
The stage is based on:
- The size (width) of the growth
- How deeply it has grown beneath the top layer of skin
- Whether cancer cells have spread to nearby lymph nodes or to other parts of the body
When skin cancer spreads from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary (original) tumor. For example, if skin cancer spreads to the lung, the cancer cells in the lung are actually skin cancer cells. The disease is metastatic skin cancer, not lung cancer. For that reason, it's treated as skin cancer, not as lung cancer. Doctors sometimes call the new tumor "distant" disease.
Blood tests and an imaging test such as a chest x-ray, a CT scan, an MRI, or a PET scan may be used to check for the spread of skin cancer. For example, if a melanoma growth is thick, your doctor may order blood tests and an imaging test.
For squamous cell skin cancer or melanoma, the doctor will also check the lymph nodes near the cancer on the skin. If one or more lymph nodes near the skin cancer are enlarged (or if the lymph node looks enlarged on an imaging test), your doctor may use a thin needle to remove a sample of cells from the lymph node (fine-needle aspiration biopsy). A pathologist will check the sample for cancer cells.
Even if the nearby lymph nodes are not enlarged, the nodes may contain cancer cells. The stage is sometimes not known until after surgery to remove the growth and one or more nearby lymph nodes. For thick melanoma, surgeons may use a method called sentinel lymph node biopsy to remove the lymph node most likely to have cancer cells. Cancer cells may appear first in the sentinel node before spreading to other lymph nodes and other places in the body.
Stages of Melanoma
These are the stages of melanoma:
- Stage 0: The melanoma involves only the top layer of skin. It is called melanoma in situ.
- Stage I: The tumor is no more than 1 millimeter thick (about the width of the tip of a sharpened pencil.) The surface may appear broken down. Or, the tumor is between 1 and 2 millimeters thick, and the surface is not broken down.
- Stage II: The tumor is between 1 and 2 millimeters thick, and the surface appears broken down. Or, the thickness of the tumor is more than 2 millimeters, and the surface may appear broken down.
- Stage III: The melanoma cells have spread to at least one nearby lymph node. Or, the melanoma cells have spread from the original tumor to tissues nearby.
- Stage IV: Cancer cells have spread to the lung or other organs, skin areas, or lymph nodes far away from the original growth. Melanoma commonly spreads to other parts of the skin, tissue under the skin, lymph nodes, and lungs. It can also spread to the liver, brain, bones, and other organs.
Stages of Other Skin Cancers
These are the stages of basal cell and squamous cell skin cancers:
- Stage 0: The cancer involves only the top layer of skin. It is called carcinoma in situ.
Bowen disease is an early form of squamous cell skin cancer. It usually looks like a reddish, scaly or thickened patch on the skin. If not treated, the cancer may grow deeper into the skin.
- Stage I: The growth is as large as 2 centimeters wide (more than three-quarters of an inch or about the size of a peanut).
- Stage II: The growth is larger than 2 centimeters wide.
- Stage III: The cancer has invaded below the skin to cartilage, muscle, or bone. Or, cancer cells have spread to nearby lymph nodes. Cancer cells have not spread to other places in the body.
- Stage IV: The cancer has spread to other places in the body. Basal cell cancer rarely spreads to other parts of the body, but squamous cell cancer sometimes spreads to lymph nodes and other organs.