Background: Sentinel lymph node (SLN) biopsy techniques provide accurate nodal staging for breast cancer. In the past, complete lymph node dissection (CLND) (levels 1 and 2) was performed for breast cancer staging, although the therapeutic benefit of this more extensive procedure has remained controversial.
This study confirms that lymphatic mapping in breast cancer patients with DCIS lesions is a technically feasible and a highly accurate method of staging patients with undetected micrometastatic disease to the regional lymphatic basin. This procedure can be performed with minimal morbidity, because only one or two SLNs, which are at highest risk for containing metastatic disease, are removed. This allows the pathologist to examine the one or two lymph nodes with greater detail by using serial sectioning and CK IHC staining of the SLNs. Because most patients with DCIS lesions detected by routine H&E stains do not have regional lymph node metastases, these patients can safely avoid the complications associated with a complete axillary lymph node dissection and systemic chemotherapy. However, DCIS patients with occult micrometastases of the regional lymphatic basin can be staged with higher accuracy and treated in a more selective fashion.
In human solid cancer, lymph node status is the most important indicator for clinical outcome. Recent developments in the sentinel lymph node concept and technology have resulted in a more precise way of examining micrometastasis in the sentinel lymph node and the role of lymphovascular system in the facilitation of cancer metastasis. Different patterns of metastasis are described with respect to different types of solid cancer. Expect perhaps for papillary carcinoma and sarcoma, the overwhelming evidence is that solid cancer progresses in an orderly progression from the primary site to the regional lymph node or the sentinel lymph node in the majority of cases with subsequent dissemination to the systemic sites. The basic mechanisms of cancer metastasis through the lymphovascular system form the basis of rational therapy against cancer. Beyond the clinical patterns of metastasis, it is imperative to understand the biology of metastasis and to characterize patterns of metastasis perhaps due to heterogeneous clones based on their molecular signatures.
When metastatic melanoma overwhelms the SLN and involves NSLNs, the biologic behavior changes to portend a worse survival, regardless of the total node count positive. These data make the argument that the current N staging system should be changed to incorporate SLN vs NSLN involvement.
The most powerful predictor of survival in breast cancer is the presence or absence of lymph node metastases. Lymphatic mapping and sentinel node biopsy is a new technique that provides more accurate nodal staging compared to routine histology for women with breast cancer without the morbidity of a complete lymph node dissection. Sentinel lymph node biopsy is a more conservative approach to the axilla that requires close collaboration between the surgical team, nuclear medicine, and pathology. National trials are investigating the clinical relevance of the upstaging that occurs with a more intense examination of the sentinel node. Since complaints due to the axillary node dissection are a common occurrence after definitive breast cancer surgery, if the side effects of the level I and II node dissection can be avoided, particularly in the node-negative population, a major advance in treating this disease will be made.
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