الفهرس 
Cervical Lymph Node GroupsOnly 14 pages are availabe for public view
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Abstract
Head and neck cancers (HNC) are dominated by squamous cell carcinomas originated from the epithelium of the upper aerodiagestive tract. The initial route of metastases is, in most cases, via lymphatics to the regional nodes of the neck. The presence of cervical metastases (N1-N3) is the most important prognostic factor in head and neck cancer patients, the presence of a single ipsilateral or contralateral metastatic node reduces survival by 50% and bilateral disease by a further 50% .
The majority of cancer mortality is due to metastatic disease rather than primary tumors. Lymph node metastasis characterizes tumors that are more aggressive and indicates the likelihood of distant metastasis.
The management of N+ head and neck squamous cell carcinoma is relatively clear-cut . By contrast, the investigation and treatment of patients with clinically N0 disease is controversial .
The clinically negative (N0) neck is defined by its absence of palpable or radiographically suspicious lymph nodes , however occult metastases may exist in approximately 15 to 40 % of these patients, so accurate staging at the time of diagnosis is critical for selection of the appropriate treatment strategy.
Perhaps the most controversial issue in the management of patients with SCC of the head and neck is whether or not to treat the cervical lymph nodes in a patient who presents with a clinically negative neck. The second issue debated is, what is the optimal management for this group of patients avoiding morbidity resulted from unnecessary neck dissection.
Although there are no universally accepted guidelines, the predominant opinion is that a patient with a clinically N0 neck should have a neck dissection, if the risk of occult metastasis is more than approximately 15–20% ,even though it will be unnecessary in the majority (80%) of cases.
Currently, despite improvements in imaging using ultrasound, CT, MRI, and PET scanning, SLNB is the only investigation that can detect micrometastatic disease.
Some authors have suggested that patients with negative results using the most accurate imaging studies, such as CT or PET-CT, could be candidates to a wait-and-see policy.
The need for a better diagnostic technique to identify subclinical cervical metastases and guide the treatment of these patients ultimately has lead to the development of SLN biopsy.
Sentinel node biopsy is an alternative to elective neck dissection for the management of T1/T2 oral and oro-pharyngeal squamous cell carcinomas and is also finding application to head and neck cancer at other sites. The main clinical aim of sentinel node biopsy is to achieve better staging and there is now evidence that the procedure reduces morbidity.
The validity of the concept of SLNB is based on the fact that if the sentinel node is free of metastasis, then other more distal nodes are also disease free.
Sentinel lymph node biopsy is a minimally invasive technique , performed in conjunction with radiotracer injection and preoperative lymphoscintigraphy followed by the intraoperative use of a hand-held gamma probe . This allows the surgeon to identify and excise targeted upper echelon lymph nodes that drain the site of a primary malignancy for the laboratory detection of what would otherwise be subclinical nodal metastases . This technique offers a less invasive means of staging lymphatic basins in a patient with a primary malignancy, and permits detailed histological , immunohistochemical and molecular examination of at least the first echelon (frequently second and rarely third) lymph node basin for clinically occult micro- and conventional metastases (clinical stage N0).
If immediate assessment of lymph nodes using frozen section or molecular biological techniques reliably show a sentinel lymph node metastasis, a neck dissection can be performed at the same sitting.
Many components have been described to be used in SLN identification such as methylene blue , Technetium 99-labelled sulfa colloid , Lymphoseek and Tc-99m-labeled human serum albumin colloid (HSA) (Nanocoll®) (GE Healthcare).
The use of lymphoscintigraphy with Tc99 m colloid as well as a following SLN biopsy with possible concurrent blue dye injection can be regarded as the current gold standard with regards to identification of the SLN.
The use of step-serial sectioning and immunohistochemistry can significantly improve the negative predictive value of the technique.
The gold standard of hematoxylin and eosin staining on formalin fixed , paraffin embedded nodes with immunohistochemistry to detect small tumor deposits is much more accurate , but takes several days to perform and thus cannot be performed intraoperatively .
The development of a fully automated and integrated RNA isolation and quantitative PCR instrument called the GeneXpert (Cepheid, Sunnyvale, CA). The GeneXpert is capable of performing RNA isolation from lysed tissue, reverse transcription, and quantitative PCR all in ∼30 minutes.
This rapid (35 minutes) , highly accurate qRT-PCR technique may facilitate more routine application of minimally invasive techniques to stage the neck, such as SNB, and direct more appropriate use of neck dissection in HNSCC patients.
Instead of running the risk of having the patient potentially return back for surgery in the case that IHC staining picks up metastatic disease, one can run the GeneXpert assay in less than 35 minutes intraoperatively, providing over 94% accuracy that the SLN is free of tumor. The high negative predictive value is of greatest clinical importance, and was the primary clinical end point of the recently published ACOSOGSLN trial , because it saves those patients free of disease from having a more extensive END which has nearly the same negative predictive value .