Abstract: Objective We studied the pattern of lymphatic metastasis in clinical N0 stage (cN0) papillary thyroid carcinoma (PTC) through an analysis of published studies to establish evidence-based guidelines for selecting and delineating clinical target levels of prophylactic lymphadenectomy. Methods The PubMed, Embase, Cochrane, and Medline databases were searched for relevant articles. The patients included were mainly untreated cN0 PTC cases that underwent thyroidectomy and prophylactic lymphadenectomy. The data were analyzed by Stata 10.2. Results A literature search yielded 6 studies. Resulting 57% of the cN0 PTC cases presented with central compartment metastasis, and 40% presented with lateral compartment metastasis. The most commonly involved regions include level VI and level III, with lymphatic metastasis rates of 57% and 42%, respectively, followed by level IV, level II, level V, level VII, and level I, with metastasis rates of 21%, 10%, 6%, 2%, and 2%, respectively. Conclusions Our analysis indicated that levels III and IV in cN0 PTC cases are high-risk, levels II and IV are moderate-risk, and levels I, VII, and V are low-risk. Clearance of levels III and IV during prophylactic neck dissection is essential for the complete removal of occult metastatic lymph nodes.

Key words: Papillary thyroid carcinoma, Lymphatic metastasis.