title: The prognostic value of the metastatic lymph node ratio and maximal metastatic tumor size in pathological N1a papillary thyroid carcinoma.
abstract: OBJECTIVE
  The presence of central neck lymph node (LN) metastases (defined as pN1a according to Tumor Node Metastasis classification) in papillary thyroid cancer (PTC) is known as an independent risk factor for recurrence. Extent of LN metastasis and the completeness of removal of metastatic LN must have an impact on prognosis but they are not easy to measure. Moreover, the significance of the size of metastatic tumors in LNs has not been clarified. This study was to evaluate the impact of the extent of LN metastasis and size of metastatic tumors on the recurrence in pathological N1a PTC.
  
  
  METHODS
  This retrospective observational cohort study enrolled 292 PTC patients who underwent total thyroidectomy with central neck dissection from 1999 to 2005. LN ratio was defined as the number of metastatic LNs divided by the number of removed LNs, which was regarded as variable reflecting both extent of LN metastasis and completeness of resection, and LN size as the maximal diameter of tumor in metastatic LN.
  
  
  RESULTS
  The significant risk factors for recurrence in univariate analysis were large primary tumor size (defined as larger than 2 cm), high LN ratio (defined as higher than 0.4), and presence of macrometastasis (defined as larger than 0.2 cm). Age, sex, clinical node status, and microscopic perithyroidal extension had no effect on recurrence. In multivariate analysis, high LN ratio and presence of macrometastasis were independent risk factors for recurrence.
  
  
  CONCLUSIONS
  LN ratio and size of metastatic nodes had a significant prognostic value in pathological N1a PTC. We suggest that risk stratification of pathological N1a PTC according to the pattern of LN metastasis such as LN ratio and size would give valuable information to clinicians.
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Republic of Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Jeon
authors.forename: Jong Ho
authors.initials: JH
authors.lastname: Yoon
authors.forename: Ji Min
authors.initials: JM
authors.lastname: Han
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Yim
authors.forename: Suck Joon
authors.initials: SJ
authors.lastname: Hong
authors.forename: Dong Eun
authors.initials: DE
authors.lastname: Song
authors.forename: Jin-Sook
authors.initials: JS
authors.lastname: Ryu
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Kim
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
authors.forename: Won Bae
authors.initials: WB
authors.lastname: Kim
mesh_terms: D000328:Adult; D002291:Carcinoma, Papillary / Q000473:pathology* / Q000601:surgery; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology* / Q000601:surgery; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000473:pathology / Q000601:surgery; D037981:Neck Dissection; D011379:Prognosis; D012008:Recurrence; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery; D013965:Thyroidectomy; D047368:Tumor Burden