It is well known that poorer prognosis prevails in head and neck cancer patients that develop metastatic lymph nodes and even more so if there is evidence of extra capsular spread. This is one of the reasons why elective neck dissections are frequently performed even in patients with N0 necks .
There are no clear and accurate guidelines regarding the decision to perform a neck dissection concurrent to the ablation of the primary tumor in the N0 neck. Clinical staging of the neck by manual examination is notoriously inaccurate, especially in patients with more voluminous necks. Radiological staging with either CT or MRI has improved the sensitivity for identifying nodal metastatic disease and has contributed to the upstaging of necks in a significant number of patients, resulting in a more accurate selection of patients requiring a neck dissection. With size alone as one of the more important criteria in this regard it has been shown that an important group of patients at risk for occult lymphatic metastasis may be missed [2, 3].
The potential benefit of CT-PET in the pre operative evaluation of patients with a negative CT or MRI is still controversial and probably plays a bigger role in detecting second primary tumors and follow up [4, 5].
Ultrasound with simultaneous fine needle aspiration cytology is probably the most accurate method to date in staging the neck, but requires skill and solid ultrasound and cytology knowledge to reach good levels of accuracy .
Currently there is thus no accurate way of determining the presence of occult lymphatic metastasis for cancers of the head and neck. It is clear that the gold standard for detecting involved lymph nodes is accurate pathological analysis of the nodes. This is traditionally done in a retrospective manner by sending the neck dissection specimen for analysis. In the normal pathological processing there is a possibility to miss micro metastases as the specimens are not as accurately examined as with a sentinel node protocol. In such a protocol stepwise serial sectioning as well as immunohistochemistry will be able to find occult microscopic deposits that would be missed with routine pathology examinations .
Many factors determine the propensity of a tumor to disseminate its cells to spread via the anatomical lymphatic system. Tumor cell motility as well as lymphatic vessel density is factors that may contribute to the enhanced spread along lymphatic pathways .
The principle of sentinel lymph node (SLN) identification and biopsy is to identify the first station of drainage of a particular anatomical area in which the tumor lies [9, 10].
SLN detection was first used in other anatomical areas like the breast and soon skin cancer as well as gastric cancers followed. In many centers SLN detection has become standard clinical practice.
Benefits for the patients are the more selective removal of the first drainage lymph nodes from a particular anatomical site with lower morbidity and by closer histological examination of the nodes a higher detection rate of micro metastasis is possible.
The anatomical basis of head and neck cancer nodal drainage has been well established and is in use on a daily basis . On this basis the type as well extent of the neck dissection is determined . For a long time the head and neck area has escaped the concept of sentinel neck dissection due to the conceived variability in the lymph drainage from the oropharyngeal area. In recent years this concept has made way for increasing interest in the potential benefits in patients with oropharyngeal cancer.
SLN identification and biopsy has increased its role in detection of the first nodal drainage in an attempt to either limit surgical damage, or to more accurately stage the patient by more accurate examination of the sentinel node or nodes. Koch et al (1998) was the first to describe the use of technesium-99 m (99T cm) labeled sulfur colloid in the quest for accurate sentinel node biopsy .
The use of lymphoscyntography with 99T cm 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 . With this technique there is no direct visualization of the lymph drainage pattern, but only indirect visualization of the SLN with the gamma probe. Indocyanin Green (ICG) has been used extensively in the medical field since 1957 . Initial uses were for blood flow measurements, but of late one of the mainstay uses is for retinal angiography, especially in the diagnosis of wet age related macular degeneration. As soon as ICG is infused intravenously, it rapidly binds to plasma proteins and thereby is confined to the vascular space. ICG is removed exclusively by the liver at the rate of 18-24% per minute so the elimination of ICG follows an exponential curve with a half-life of ~150-180 s .
The use of ICG in the diagnosis of SLN in areas other than that of the head and neck region has well been described. Reports of its use in gastric, breast, lung as well as skin cancer are found in the literature with good success [17–22]