Impact Of Lymph Node Metastasis Risk Factors On Neck Dissection Choice For Papillary Thyroid Carcinoma

Background: Papillary thyroid carcinoma (PTC) is the most common form ofendocrine malignancy with a tendency of cervical lymphatic spread despite therelatively excellent prognosis. Impact of cervical lymph node metastasis (LNM)on recurrence and mortality has been demonstrated by masses of evidences,emphasizing the significance of neck dissection for thyroid surgery. Greatfocus has been paid on the choice of cervical neck dissection by manysurgeons to achieve definite tumor resection with low operative morbidity andhigh quality of postoperative survival.Objective: Risk factors have been analyzed to explore the regularity of itsimpact on lymph node metastasis in order to provide effective reference forneck dissection.Methods: This retrospective study involved1480PTC patients who underwentprimary thyroidectomy and cervical neck dissection from January2009toDecember2011in China-Japan Union Hospital of Jilin University. Differentgroups were divided according to dissection procedures for statisticalcomparison of gender, age, focal number, tumor size, and tumor location.Regularity of the impacts were observed to identify their evaluationalsignificance for lymph node metastasis and dissection choice.Results:①601cases of LNM were diagnosed by pathological section withratio of40.6%. Incidences of node involvement was32.09%(475/1480) atlevel Ⅵ and32.08%(374/1166) at level Ⅱ-Ⅳ, which were almost the same.②37.2%female patients showed LNM compared with54.5%in male.③LNMappeared an increasing tendency along with the decreasing of age with a highrates of77.5%in patients younger than30. Incidences in different age groupswere all above70%in level Ⅵ although it was affected by age statistically.④Unifocal and multifocal rates of LNM were37.2%and46.4%respectively (P<0.01), which were not associated with transfer position.⑤Patients withtumor size>1cm showed much higher incidence of LNM (63.8%) thanmicrocarcinoma.⑥Approximately half of lateral metastasis appeard inipsilateral lymph node (48.7%on the left and50.9%on the right), whereasrare ipsilateral involvement (4.4%on the left and3.6%on the right) wasseen when no primary lesion was found in the same side of thyroid lobe.⑦Predictive value of level Ⅵ and level Ⅱ-Ⅳ are similar (level Ⅵ to levelⅡ-Ⅳ is64.8%,level Ⅱ-Ⅳ to level Ⅵ is66.3%）, skip metastasis rate is16.1%.Conclusion:1. Gender, age, focal number, tumor size and tumor locationhave significant influence on LNM of PTC. LNM rate is higher among patientswith characteristics of male, younger age, multifocal lesion, large tumor sizeand lobe involvement.2. Risk of lateral metastasis is high in patients withtumor size above1cm with ipsilateral cervical compartment to be the mostcommon involved site.3. Incidences of node involvement in level Ⅵ and levelⅡ-Ⅳ are both significant which have relationship between each other. Level Ⅴmetastasis is not common even in clinical positive patients of this area whilelevel Ⅶ positive is rather rate.4. Prophylactic central and ipsilateral necklymph node dissection is recommended routinely during the primary treatmentof PTC patients whereas level Ⅴ and level Ⅶ should be performed only inpatients with preoperative suspected and/or intraoperatively proven LNM.