Sentinel lymph node

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sentinel lymph nodes
. The axillary lymph nodes drain 75% of the lymph from the breasts((uncited)) and so may be the first lymph nodes affected in breast cancer.

The sentinel lymph node is the hypothetical first

tumor
.

The sentinel node procedure (also termed sentinel lymph node biopsy or SLNB) is the identification, removal and analysis of the sentinel lymph nodes of a particular tumour.[1]

Physiology

The spread of some forms of cancer usually follows an orderly progression, spreading first to regional lymph nodes, then the next echelon of lymph nodes, and so on, since the flow of lymph is directional, meaning that some cancers spread in a predictable fashion from where the cancer started. In these cases, if the cancer spreads it will spread first to lymph nodes (lymph glands) close to the tumor before it spreads to other parts of the body. The concept of sentinel lymph node surgery is to determine if the cancer has spread to the very first draining lymph node (called the "sentinel lymph node") or not. If the sentinel lymph node does not contain cancer, then there is a high likelihood that the cancer has not spread to any other area of the body.[2]

Uses

The concept of the sentinel lymph node is important because of the advent of the sentinel lymph node biopsy technique, also known as a sentinel node procedure. This technique is used in the staging of certain types of cancer to see if they have spread to any lymph nodes, since lymph node metastasis is one of the most important prognostic signs. It can also guide the surgeon to the appropriate therapy.[3]

A blue stained sentinel lymph node in the axilla.
A micrograph showing an adenocarcinoma of the breast (dark pink) in a lymph node (purple) and extending into the surrounding fat (white, chicken-wire appearance). H&E stain.

There are various procedures entailing the sentinel node detection:

In everyday clinical activity, entailing sentinel node detection and sentinel lymph node biopsy, it is not required to include all different techniques listed above. In skilled hands and in a center with sound routines, one, two or three of the listed methods can be considered sufficient.

To perform a sentinel lymph node biopsy, the physician performs a lymphoscintigraphy, wherein a low-activity

pathologist for rapid examination under a microscope
to look for the presence of cancer.

A frozen section procedure is commonly employed (which takes less than 20 minutes), so if neoplasia is detected in the lymph node a further lymph node dissection may be performed. With malignant melanoma, many pathologists eschew frozen sections for more accurate "permanent" specimen preparation due to the increased instances of false-negative with melanocytic staining.

Clinical advantages

There are various advantages to the sentinel node procedure. First and foremost, it decreases lymph node dissections where unnecessary, thereby reducing the risk of

renal cell cancer.[17][18]

Research advantages

As a bridge to translational medicine, various aspects of cancer dissemination can be studied using sentinel node detection and ensuing sentinel node biopsy. Tumor biology pertaining to metastatic capacity,[19] mechanisms of dissemination, the EMT-MET-process (epithelial–mesenchymal transition) and cancer immunology[20] are some subjects which can be more distinctly investigated.

Disadvantages

However, the technique is not without drawbacks, particularly when used for melanoma patients. This technique only has therapeutic value in patients with positive nodes.[21] Failure to detect cancer cells in the sentinel node can lead to a false negative result—there may still be cancerous cells in the lymph node basin. In addition, there is no compelling evidence that patients who have a full lymph node dissection as a result of a positive sentinel lymph node result have improved survival compared to those who do not have a full dissection until later in their disease, when the lymph nodes can be felt by a physician. Such patients may be having an unnecessary full dissection, with the attendant risk of lymphedema.[22]

History

The concept of a sentinel node was first described by Gould et al. 1960 in a patient with cancer of the parotid gland[23] and was implemented clinically on a broad scale by Cabanas in penile cancer.[24] The technique of sentinel node radiolocalization was co-founded by James C. Alex, MD, FACS and David N. Krag MD (University of Vermont Medical Center) and they were the first ones to pioneer this method for the use of cutaneous melanoma, breast cancer, head and neck cancer and Merkel cell carcinoma. Confirmative trials followed soon after.

Moffitt Cancer Center with Charles Cox, MD, Cristina Wofter, MD, Douglas Reintgen, MD and James Norman, MD
. Following validation of the sentinel node biopsy technique, a number of randomised controlled trials were initiated to establish whether the technique could safely be used to avoid unnecessary axillary dissection among women with early breast cancer. The first such trial, led by Umberto Veronesi at the European Institute of Oncology, showed that women with breast tumours of 2 cm or less could safely forgo axillary dissection if their sentinel lymph nodes were found to be cancer-free on biopsy.[26] The benefits included less pain, greater arm mobility and less swelling in the arm.[27]

See also

  • ALMANAC, Axillary Lymphatic Mapping Against Nodal Axillary Clearance trial

References

  1. S2CID 242176779
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  7. ^ "Sentimag". Endomag. Retrieved 2019-03-09.
  8. ^ BNMS (August 2011). "Lymphoscintigraphy Clinical Guidelines" (PDF). Retrieved 3 January 2017.
  9. PMID 11314938
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  21. ^ Wagman LD. "Principles of Surgical Oncology" in Pazdur R, Wagman LD, Camphausen KA, Hoskins WJ (Eds) Cancer Management: A Multidisciplinary Approach Archived 2013-10-04 at the Wayback Machine. 11 ed. 2008.
  22. S2CID 7068382
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  26. ^ Veronesi, Umberto et al. (2006) Sentinel-lymph-node biopsy as a staging procedure in breast cancer: update of a randomised controlled study. Lancet Oncol 7:983‒990 doi:10.1016/S1470-2045(06)70947-0
  27. ^ Veronesi, Umberto et al. (2003) A Randomized Comparison of Sentinel-Node Biopsy with Routine Axillary Dissection in Breast Cancer. N Engl J Med 349:546-553 DOI:10.1056/NEJMoa012782

Further reading

External links