Sentinel Node Dissection

The technology and indications for sentinel node dissection have continued to expand over the last several years. It is used routinely for intermediate thickness melanoma and Merkel cell carcinoma, and has been used for cutaneous squamous cell carcinoma of the head and neck. Sentinel node biopsy has been shown to be a reliable staging technique for intermediate thickness oral cavity cancer, with sensitivity and negative predictive value rates mirroring those for melanoma. Its use in pharyngeal and laryngeal cancer continues to be investigated. The use of Tc-99m tilmanocept, a CD206 receptor target, allows for more specificity for the first echelon sentinel lymph nodes and may result in improved accuracy and a lower false-negative rate. The widespread availability and accuracy of combined SPECT/CT imaging provides a scrollable three-dimensional analysis of the drainage basins, resulting in better targeted dissections and patient counseling. Despite these technological advances, the use of the gamma probe for sentinel node dissection is not always intuitive and requires specific training and expertise, especially in cutaneous lesions that show frequent metastases to the parotid gland. Serial step sectioning and immunohistochemistry analysis are critical to the detection of micrometastases. Intraoperative frozen section analysis has also shown great promise for identifying sentinel nodes in oral cavity squamous cell carcinoma, allowing for completion lymphadenectomy in the same setting. Sentinel node biopsy and dissection remains an intriguing prognostic and potentially therapeutic option for malignancies with an intermediate risk of regional metastases, with increased diagnostic information compared to watchful waiting with serial imaging but sparing the morbidity of a full elective neck dissection in patients who end up with microscopically negative lymphatic basins.