Melanoma is a type of skin cancer that begins in melanocytes, the cells responsible for producing skin pigment. While it is less common than other skin cancers, melanoma is considered more serious due to its ability to spread from its original site. This spread often involves the lymphatic system, a network of vessels and organs that are part of the body’s immune defense.
The Role of Lymph Nodes in Melanoma Spread
Lymph nodes are small, bean-shaped organs distributed throughout the body, including the neck, armpits, and groin. They serve as filters for lymph fluid, a clear liquid that circulates throughout the body, carrying immune cells and waste products. Lymph nodes contain specialized immune cells, such as lymphocytes, which identify and fight off foreign substances like bacteria, viruses, and even cancer cells.
Melanoma cells can detach from the primary tumor and enter the lymphatic vessels. These vessels then transport the cancer cells to nearby lymph nodes. The initial lymph node or nodes that receive drainage from the area of the primary tumor are called sentinel lymph nodes. If melanoma cells are found in these sentinel nodes, it indicates the cancer has progressed beyond its original location.
Key Factors Influencing Spread Rate
Melanoma spread to lymph nodes is influenced by several tumor characteristics. The depth of the melanoma, measured as Breslow thickness, is a significant factor. Thicker melanomas, meaning those that have grown deeper into the skin, have a higher likelihood of spreading to the lymph nodes.
The presence of ulceration, which is an open sore on the melanoma, also suggests a more aggressive tumor that is prone to spread. Another indicator is the mitotic rate, which reflects how quickly the cancer cells are dividing and multiplying. A higher mitotic rate suggests faster tumor growth and a greater potential for spread.
Melanoma cells found within lymphatic or blood vessels, known as lymphovascular invasion, are also associated with an increased risk of spread to lymph nodes and a less favorable outlook. The location of the tumor can also play a role, as different body areas have distinct lymphatic drainage patterns. A patient’s age and immune system strength can also influence the disease’s course.
How Lymph Node Spread is Diagnosed
Determining if melanoma has spread to lymph nodes often begins with a clinical examination. A doctor may physically check the lymph nodes for any signs of enlargement or tenderness. However, enlarged nodes are not always indicative of cancer, and nodes can contain microscopic cancer cells without being noticeably swollen.
A key diagnostic procedure is the Sentinel Lymph Node Biopsy (SLNB). This procedure identifies whether cancer cells have reached the first lymph node(s) draining the primary tumor.
During an SLNB, a radioactive tracer and/or a blue dye are injected near the site where the melanoma was removed. These substances travel through the lymphatic vessels to the sentinel node(s) for removal. The removed nodes are then examined under a microscope for cancer cells. A negative result suggests the cancer has not spread to nearby lymph nodes; a positive result indicates spread.
Imaging tests can also be used in advanced cases to assess for lymph node involvement or distant spread. These include computed tomography (CT) scans, which provide detailed images. Positron emission tomography (PET) scans can detect areas of increased metabolic activity, indicating cancer. Magnetic resonance imaging (MRI) checks for spread to the brain or spinal cord. While these imaging techniques can reveal enlarged lymph nodes, SLNB remains important for detecting microscopic spread.
What Lymph Node Involvement Means for Treatment and Prognosis
When melanoma spreads to the lymph nodes, it significantly impacts the staging of the disease. Lymph node involvement classifies melanoma as Stage III, indicating a more advanced disease state compared to localized melanoma. This staging guides treatment decisions and understanding the disease’s course.
The presence of melanoma cells in lymph nodes generally suggests a less favorable prognosis compared to melanoma that has not spread beyond the primary site. While survival rates vary, lymph node involvement increases the risk of recurrence or further spread.
Treatment approaches for melanoma with lymph node involvement involve combination therapies. Surgery to remove affected lymph nodes, known as lymphadenectomy, may be performed. Additionally, adjuvant therapies are frequently recommended after surgery to reduce the risk of recurrence. These systemic treatments, such as immunotherapy or targeted therapy, destroy any remaining microscopic cancer cells. Ongoing surveillance with physical exams, imaging studies, and blood tests is also an important part of managing melanoma with lymph node involvement.