Like other forms of cancer, melanoma can spread from the site of the original tumor throughout the body (this spreading is called “metastasis”). Melanoma may travel in three different ways. It can spread through tissue (growing from its original site into neighboring areas) or spread by blood (traveling through blood vessels throughout the body).

The third way that melanoma may spread is via the lymphatic system, which is a network of organs and vessels that produce and circulate lymph, a clear liquid containing white blood cells. In the case of melanoma, cancer cells can break away from the original tumor, enter the nearest lymph node (called a sentinel lymph node), and travel through lymph vessels to form a new tumor (called a metastatic tumor) elsewhere in the body.

Sentinel Lymph Node Biopsy

In order to help determine the extent to which melanoma may have spread, your doctor may order a sentinel lymph node biopsy (SLNB), which is a surgical procedure used to discover whether cancer cells have travelled to one or more lymph nodes near the original cancer site.

This procedure involves locating and removing the sentinel node and studying it in a laboratory. The results of this test will help your doctor decide how best to treat the cancer.