One of the concerns in treating skin cancer is knowing which patients are at risk of having melanoma spread to other parts of the body. These patients should be treated aggressively in order to stop the advance of skin cancer. Other patients undergo needless surgery and treatment because, while they have cancer, it won’t spread. The problem, though, is that doctors don’t have any way of knowing the difference - and therefore would prefer to err on the side of caution and treat everyone as if the cancer may spread.
In a previous post, we introduced research on a blood test which researchers are working on that will detect the spread of melanoma and allow for quicker treatment to those at risk. This is an important step. Another research study has identified a way to biopsy lymph nodes to detect if the cancer has the potential to spread.
Scientists in Italy found that testing immune cells in the sentinel lymph node provides information on how aggressive the cancer is. You have lymph nodes in different areas throughout your body. Sentinel lymph nodes are those closest to the cancer site. While the researchers admit there were a small number of participants in the study (42 patients with melanoma and 25 healthy participants), the results are still promising and provides "proof-of-principle that the immune system is crucially involved in controlling tumor growth, and that sentinel nodes are endowed with precise information on cancer behavior." 
Specifically, the researchers found that those patients whose sentinel nodes contained a subset of cells, called CD30-positive T cells, were more likely to see spread of their cancer within five years. This type of cell was also found in the lymph nodes and blood of patients with previously diagnosed aggressive melanoma. By further developing this information, doctors may be able to test patients to determine if they are at risk for melanoma spreading to other parts of the body and develop a more aggressive treatment plan. In addition, the information might help to reduce the treatment for patients without these specific cells, thereby reducing unneeded surgery and treatment for some patients.
In addition, researchers believe this information can help doctor create a more personalized treatment plan - specifically targeting the CD30 cells. "Considering that drugs directed against this molecule have recently been developed to treat lymphoma, this hypothesis might be easily tested in the near future." 
"New Biopsy Test Could Pick Out Aggressive Form of Skin Cancer," 2014, Jan 8, Markus MacGill, Medical News Today