title: Impact of microscopic extra-nodal extension (ENE) on locoregional recurrence following curative surgery for papillary thyroid carcinoma.
abstract: BACKGROUND
  The presence of microscopic extra-nodal extension (ENE) may increase locoregional recurrence (LRR) in papillary thyroid carcinoma (PTC). We aimed to evaluate the association between microscopic ENE, response to initial therapy and LRR risk following total thyroidectomy, therapeutic neck dissection, and radioactive iodine (RAI) ablation in PTC.
  
  
  METHODS
  Of the 369 eligible PTC patients, 264 (71.5%) did not have microscopic ENE (group I) while 105 (28.5%) did (group II). All presented with clinical nodal metastasis (cN1) and underwent therapeutic neck dissection and RAI ablation. Biochemical incompleteness meant post-ablation stimulated thyroglobulin (sTg) >10 ng/ml. Multivariate analyses were conducted to identify independent factors for LRR.
  
  
  RESULTS
  Biochemical incompleteness was significantly more common group II (43.8% vs. 17.4%, P < 0.05). The 10-year locoregional free-survival was significantly worse in group II than I (52.0% vs. 86.2%, P = 0.005). After adjusting for other significant factors, age <45 (P < 0.05), multifocality (P < 0.05), presence of ENE (P = 0.027) were independent risk factors of LRR. The number and size of positive lymph nodes were not independent factors.
  
  
  CONCLUSIONS
  Patients with microscopic ENE were significantly more likely to have biochemical incompleteness after initial therapy. After adjusting for other significant primary and nodal characteristics, microscopic ENE was an independent factor for LRR in patients with cN1. J. Surg. Oncol. 2016;113:526-531. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Surgery, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Brian H-H
authors.initials: BH
authors.lastname: Lang
authors.affiliation: Department of Anatomical Pathology, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Tony W H
authors.initials: TW
authors.lastname: Shek
authors.affiliation: Department of Clinical Oncology, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Koon Yat
authors.initials: KY
authors.lastname: Wan
mesh_terms: D055011:Ablation Techniques; D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000473:pathology* / Q000601:surgery*; D002291:Carcinoma, Papillary; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D037981:Neck Dissection; D061206:Neoplasm Micrometastasis; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology*; D012307:Risk Factors; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery*; D013965:Thyroidectomy
keywords: ATA risk stratification; TNM staging; distant metastasis; nodal metastasis; papillary thyroid carcinoma