Effect of cellular environment on melanoma spread to lymph nodes

The authors examined the cellular environment in melanoma samples and its effect on outcome of patients.

In skin melanoma, the sentinel lymph node (SLN) is the first lymph node (tiny, bean-shaped organ that helps fight infection) to which the cancer cells are believed to spread (micrometastasis). The presence of cancer in the SLN is determined by a procedure called sentinel lymph node biopsy (SLNB). It involves taking a tissue sample to determine whether the cancer has spread to the nearby lymph nodes. The nodes which have the cancer are called positive SLN.

Other than surgical removal of the positive SLN, there is no established treatment for this micrometastasis. To develop effective therapy, understanding of the cellular environment around the lymph nodes and the impact of it in tumor progression is necessary. Natural killer cells (NK cells) are important immune cells, which have the ability to kill tumor cells naturally. Other important  immune cells include macrophages, CD34 cells and CD8⁺T cells. Evaluation of these cells in micrometastatic melanoma might help develop novel treatment in future.

The authors aimed to analyze various immune cells in melanoma that had spread to lymph nodes.

There were 2 groups of patients used in this study. Group 1 included 39 patients with primary skin melanoma. In group 2, SLN samples from 86 patients were analyzed. 23 patients had SLN positive melanoma and 63 patients had negative SLN melanoma.

In group 1, NK cells entered (infiltrated) the tumors. The number of NK cells increased with age of the patients. There was no correlation between tumor thickness (how far the cancer reached deep into the skin) and NK cell numbers. There was no correlation between NK numbers and 5 year relapse (return of cancer) rates.

In group 2, high numbers of macrophages and CD34 were found in SLN positive melanoma samples. Similar amounts of NK cells and GrzB (a protein found in NK cells) positive cells were found in both SLN positive and negative melanoma samples. Numbers of CD8⁺T cells and GrzB positive cells were correlated only in SLN negative melanoma.

48% of SLN positive patients had tumor relapse compared to 29% of SLN negative patients.

The authors concluded that infiltration of NK cells was not correlated with primary skin cancer. They further indicated that number of macrophages and CD34 cells increased in SLN positive melanoma.