Check out this answer from Consensus:
The sentinel lymph node plays a crucial role in the metastatic spread of cancer. It serves as the initial gateway for cancer cells to disseminate to distant sites. The detection and analysis of SLN metastasis are vital for accurate staging, prognosis, and treatment planning in cancer patients. Ongoing research into the mechanisms of SLN involvement in metastasis will continue to enhance our understanding and management of cancer.
Cancer metastasis is a complex process involving the spread of cancer cells from the primary tumor to distant sites in the body. The sentinel lymph node (SLN) is often the first lymph node to which cancer cells spread from a primary tumor. This article explores the role of the SLN in cancer metastasis, examining whether it serves as the main gateway for the spread of cancer.
The Role of Sentinel Lymph Nodes in Cancer Metastasis
The sentinel lymph node is the first lymph node that receives lymphatic drainage from a primary tumor. It is a critical site for the initial spread of cancer cells. Studies have shown that the SLN is a key player in the metastatic process for various types of cancers, including melanoma, breast cancer, and cervical cancer.
Mechanisms of Metastasis
Research has demonstrated that the SLN undergoes significant changes even before metastatic cells arrive. For instance, VEGF-C-induced lymphangiogenesis in SLNs promotes the expansion of lymphatic networks, facilitating the spread of cancer cells to distant sites1. This lymphangiogenesis is crucial for the metastatic process, as it prepares the SLN to receive and disseminate cancer cells.
Immune Modulation
The SLN is also subject to immune modulation by tumor cells. Tumor-induced immune changes in the SLN can inhibit the generation of tumor-specific cytotoxic T cells, thereby facilitating metastasis4. This immune suppression can be reversed by treatments such as granulocyte/macrophage colony-stimulating factor (GM-CSF), highlighting potential therapeutic strategies to combat metastasis.
Detection and Prognostic Value
Sentinel lymph node biopsy (SLNB) is a highly reliable method for detecting metastasis in early-stage cancers. It is particularly effective in breast cancer and melanoma, where it has become the standard of care for nodal staging8. The detection of metastasis in the SLN can significantly influence treatment decisions and prognostic assessments.
Clinical Studies
Several clinical studies have underscored the importance of SLNB. For example, in early cervical cancer, SLNB has shown high sensitivity and negative predictive value for detecting lymph node metastasis5. Similarly, in endometrial cancer, SLN mapping has increased the detection of lymph node metastasis, leading to more accurate staging and appropriate use of adjuvant therapies3.
Prognostic Implications
The presence of metastasis in the SLN is a strong predictor of further metastatic spread and poor prognosis. In breast cancer, extranodal extension (ENE) of SLN metastasis is associated with a higher risk of mortality and disease recurrence7. This highlights the importance of considering SLN status in the overall management and prognosis of cancer patients.
Is the sentinel lymph node the main gateway for cancer metastasis?
Stanley P. L. Leong MD has answered Likely
An expert from California Pacific Medical Center Research Institute in Cancer Metastasis, Cancer Immunology, Immunotherapy
We have recently published a paper:
Thomas DC, Han G, Leong SP, Kashani-Sabet M, Vetto J, Pockaj B, White RL, Faries MB, Schneebaum S, Mozzillo N, Charney KJ, Sondak VK, Messina JL, Zager JS, Han D.
Ann Surg Oncol. 2019 Jul;26(7):2254-2262. doi: 10.1245/s10434-019-07369-w. Epub 2019 Apr 22.
PMID: 31011906
Based on this publication by the Sentinel Lymph Node Working Group, the systemic metastatic rate of melanoma patients with a negative sentinel lymph node biopsy is only about 4% indicating that if the sentinel lymph node is negative, metastasis rate bypassing the sentinel lymph node is very low. Therefore, the data suggests that sentinel lymph node may serve as a gateway for systemic metastasis.
Is the sentinel lymph node the main gateway for cancer metastasis?
Alan Wells has answered Unlikely
An expert from University of Pittsburgh in Cancer Metastasis
In breast cancer the rate of dissemination in sentinel node negative patients is less than that of sentinel node positive, but still significant with at least some 10% showing evidence of dissemination. This suggest that the sentinel node is a reporter of ability to disseminate and not the gateway to disseminate. In other words, highly metastatic cancers have a high propensity to colonize the draining lymph nodes, but this is neither necessary nor the source of distant organ metastases.
Other cancers in which the evidence points to the limited or lack of sentinel node colonization are GI tumors disseminating to the liver.