Terminology and Classification System of Lateral Neck Node Dissection in Differentiated Thyroid Carcinoma

Lee, Young Don

Abstract

The standard radical neck dissection, introduced at the turn of the 20th century, became the uniformly-accepted treatment of cervical metastatic disease through the 1960s. Functional or modified radical neck dissection was developed in the 1950s and 1960s. This procedure became the accepted treatment for suitable tumors by the 1970s. Now, the concept of selective neck dissection, removal of only the node levels likely to be involved with tumor, gained acceptance by the late 1980s as a definitive elective, and eventually, therapeutic neck dissection for suitable cases. In response to the increasing variations of neck dissection procedures, a number of classification systems were proposed and subsequently established. The system of the American Head and Neck Society and the American Academy of Otolaryngology-Head and Neck Surgery was revised in 2002 and 2008. The neck dissections are grouped into four broad categories: radical, modified radical, selective, and extended neck dissection. The Japan Neck Dissection Study Group presented a new system for the classification of neck dissections based on a system of letters and symbols. The system permits a comprehensive and shorthand method of precise designation of neck dissection procedure, but has the disadvantage of departing radically from previously employed systems, by utilizing an entirely new terminology and designation of lymph node groups. In 2011, an international group proposed a classification which conveys precisely the extent of the lymphatic and non-lymphatic structures removed in a neck dissection. So they contended it is logical, simple, and easy to remember, and prevents possible confusion associated with the ambiguous terminology previously mentioned. And they also maintained it allows the recording of neck dissection procedures that cannot be classified under the existing systems. In 2012, the American Thyroid Association proposed the consensus of lateral neck dissection in DTC. They defined again that a selective neck dissection refers to removal of less than all five nodal levels directed by the patterns of lymphatic drainage from the primary tumor while preserving CN XI, IJV, and SCM. And they also insist that selective neck dissection is the most commonly-used neck dissection in the management of lateral neck metastasis for thyroid cancer, and should be reported with a designation of the side and nodal levels and sublevels dissected (i.e. selective neck dissection of levels IIa, III, IV, and Vb). But most classification systems have some limitations and disadvantages to describe the exact procedures of lymphatic and non-lymphatic structure resection. It is a necessary component of a new systemic classification and nomenclature system for neck dissection, not only because the method of describing operative procedures must be unified to allow comparisons of therapeutic methods, but also because of the need to customize therapies individually. A new neck dissection classification system in thyroid cancer has to overcome all these limitations and will facilitate communication around the world with reliable reporting and comparison of outcomes among different surgeons and institutions.