Head and neck sentinel lymph node biopsy: current state of the art

Abstract

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. Reported detection rates for sentinel neck nodes are greater than 95% and there is also a negative predictive value of 95% for negative sentinel nodes. Current histopathological protocols have been developed for use in the research setting and are designed to identify all micrometastatic disease. However the use of step serial sectioning at 150 micron intervals with pan-cytokeratin immunohistochemistry is currently advised and appears to upstage nodes by approximately 20% over the initial single routine stained section. Adoption of the UICC/TNM definitions is recommended for future sentinel node studies, but further refinements and descriptions are required. The SENT trial has recruited over 300 cases from 10 European centres and a quality control study of the pathological material is in progress. At the first consensus meeting of the SENT pathology group there were excellent levels of agreement on the diagnosis of positive and negative nodes, and a number of potential pitfalls such as non-malignant inclusions and staining artefacts were identified.

Fig. 1

AE1/AE3 stained section showing individual nucleated tumour cells related to the lymph node sinus in a sentinel node

Fig. 2

Group of squamous carcinoma cells in a lymphatic vessel outside a node. This was only seen in one level and illustrates a limitation of the pathology protocol. If section quality is poor at any level, there is no opportunity to examine further material from the block

Fig. 3

Group of suspicious cells close to the periphery of a sentinel node. These cells proved to be cytokeratin negative and were confirmed as macrophages by further immunohistochemistry

Fig. 4

Cytokeratin positive artefacts. Dendritic cells stained by AEI/AE3 and extrinsic positively stained desquamated squames are commonly encountered in sentinel node preparations