Classification of locoregional lymph nodes in medullary and papillary thyroid cancer

Among the various thyroid malignancies, medullary and papillary thyroid carcinomas are characterized by predominant locoregional lymph node metastases that may cause morbidity and affect patient survival. Although lymph node metastases are frequently detected, the optimal strategy aiming at the removal of all tumor tissues while minimizing the associated surgical morbidity remains a matter of debate.

A uniform consented terminology and classification is a precondition in order to compare results of the surgical treatment of thyroid carcinomas. While the broad distinction between central and lateral lymph node groups is generally accepted, the exact boundaries of these neck regions vary significantly in the literature. Four different classification systems are currently used. The classification system of the American Head and Neck Society and the corresponding classification system of the Union for International Cancer Control (UICC) are based on observations of squamous cell carcinomas and appointed to needs of head and neck surgeons. The classification of the Japanese Society for Thyroid Diseases and the compartment classification acknowledge the distinctive pattern of metastasis in thyroid carcinomas.

Comparison of four existing classification systems reveals underlying different treatment concepts. The compartment system meets the necessities of thyroid carcinomas and is used worldwide in studies describing the results of lymph node dissection. Therefore, the German Association of Endocrine Surgery has recommended using the latter system in their recently updated guidelines on thyroid carcinoma.