The prognostic implications of microsatellitosis in melanoma patients

This article investigated the prognostic value of microsatellitosis and lymph node metastasis in patients with melanoma. 

Melanoma is a type of malignant skin cancer that arises in melanocytes (cells that give skin its color). This type of cancer has a high tendency to metastasize (spread) into lymph nodes. The first lymph nodes into which cancer cells spread are called sentinel lymph nodes and in order to identify them, a procedure called sentinel lymph node biopsy is performed. The biopsy removes these nodes during surgery and analyzes them under a microscope for cancer cells. This can allow identification of many features that can help predict the likely outcome of the disease (prognosis).  

Another feature associated with melanoma is microsatellites; tiny melanoma cells near the main tumor that can only be seen with a microscope. These are considered a high risk feature for lymph node metastasis. Melanomas may also present with ulceration, in which the tumor’s top skin layer is broken and is an indicator of metastatic potential. The great variability of these features influences the severity of the disease and creates prognostic diversity.

The present study included 1,621 melanoma patients who underwent sentinel lymph node biopsy and compared patients with (98) and without (1,523) microsatellitosis. Analysis of each biopsy included: tumor thickness, Clark level  (a staging system describing how deep the melanoma invades the skin), tumor infiltrating lymphocytes (white blood cells, cells of the immune system that have migrated into a tumor and are associated with better prognosis), lymphovascular invasion  (the spread of a cancer to the blood vessels and/or lymphatics), ulceration  and microsatellitosis.

Diagnosis of microsatellitosis was associated with additional aggressive features of the primary tumor including increased tumor thickness, higher Clark level, lymphovascular invasion and ulceration. The frequency of lymph node metastasis was significantly higher in patients with microsatellitosis (43%) versus patient without (11%).

The 5-year melanoma-specific survival rate (percentage of patients who had not died from melanoma) was 68% in patients with microsatellitosis. Ulceration, lymphovascular invasion and metastasis to more than one lymph node were all associated with decreased melanoma-specific survival. However, the absence of ulceration and metastasis to only one lymph node was associated with a melanoma-specific survival rate of 90% in a small subset of patients with microsatellitosis.  The 5-year overall survival rate (the percentage of patients that were alive five years after their diagnosis) was 64%. 

Overall, patients with microsatellitosis had worse prognosis. However, microsatellitosis in the absence of additional adverse features had a more favorable prognosis.

This study included an uneven number of patients between the groups which may have affected the results.