Role of sentinel lymph node biopsy in oral cancer

Squamous cell carcinoma of the oral cavity represents about 2% of all malignant neoplasms and 47% of those developing in the head and neck area. The tongue is the most common site involved, and this incidence is increasing mainly in young people, possibly related to human papilloma virus infections. Prognosis depends on the stage: the 5-year survival rate of tongue squamous cell carcinoma, whatever the T stage, is 73% in pN0 cases, 40% in patients with positive nodes without extracapsular spread (pNl ECS-), and 29% when nodes are metastatic with extracapsular spread (pNl ECS+: p > or = 0.0001). Nodal micrometastases (cN0 pN1) are found in up to 50% of cN0 tongue squamous cell carcinoma patients operated on the neck. At present, no clinical, imaging staging modalities or biological markers are available to diagnose nodal micrometastases. The sentinel node biopsy has been tested since 1996 in order to find a solution to this problem. The sentinel node is the first node reached by the lymphatic stream, assuming an orderly and sequential drainage from the tumour site, and should be predictive of the nodal stage. According to the literature, sentinel node biopsy is a reliable technique in selected cN0 cases, but the procedure is still experimental and should not be performed outside validation trials. Successful application of sentinel node biopsy in the head and neck region requires surgical experience and specific technical devices, including pre-operative lymphoscintigraphy and intra-operative gamma-probe. Moreover, dynamic lymphoscintigraphy seems to be able to show the lymphatic stream from the primary tumour and could allow a selective neck dissection to be tailored thus reducing the related morbidity.