title: Threshold primary tumour sizes for nodal and distant metastases in papillary and follicular thyroid cancers.
abstract: BACKGROUND
  In papillary and follicular thyroid cancers (PTC, FTC), nodal and distant metastasis are generally considered important determinants of recurrence and survival, respectively. However, there is no consensus about the threshold primary tumour size (PTS) for these determinants. The aim of this study was to assess size relationships for developing nodal, pulmonary, bone and overall distant metastases.
  
  
  METHODS
  This prospective study covered 139 (93 females and 46 males) consecutive biopsy proven patients with PTC (114/139, mean age 41.0 ± 15.7 years, M: F, 35%:65%) and FTC (25/139, mean age 39.2 ± 14.3 years, M: F: 24%:76%).
  
  
  RESULTS
  Average primary tumor size was 23.4 ± 11.1 mm and 26.5 ± 13.1 mm for PTC and FTC respectively (p value=0.223). Nodal metastasis was found more common in PTC than FTC (49% vs 28%, p value <0.05), whereas overall distant metastasis was approximately the same (13% and 24%, p value =0.277); however, bone metastasis was significantly higher in FTC than PTC (24% vs 5%, p value <0.05). Cumulative risk for nodal and distant metastases for FTC and PTC starts at PTS <20 mm and may indicate an unusual aggressive tumor behavior in the studied population. Highest cumulative risk for nodal and pulmonary metastases in PTC and for bone metastasis in FTC was found to be ≥ 50 mm PTS.
  
  
  CONCLUSIONS
  We conclude that a PTS of <20 mm may indicate an unusual aggressive tumor behavior with highest cumulative risk for nodal and pulmonary metastases in PTC and for bone metastasis in FTC with a cutoff of ≥ 50 mm.
authors.affiliation: The Aga Khan University Hospital (AKUH), Karachi, Pakistan. maseeh.uzzaman@aku.edu
authors.forename: Maseeh uz
authors.initials: Mu
authors.lastname: Zaman
authors.forename: Nosheen
authors.initials: N
authors.lastname: Fatima
authors.forename: Zafar
authors.initials: Z
authors.lastname: Sajjad
authors.forename: Jaweed
authors.initials: J
authors.lastname: Akhtar
authors.forename: Najmul
authors.initials: N
authors.lastname: Islam
authors.forename: Qamar
authors.initials: Q
authors.lastname: Masood
authors.forename: Asma
authors.initials: A
authors.lastname: Ahmed
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000473:pathology*; D000328:Adult; D002277:Carcinoma / Q000473:pathology*; D002291:Carcinoma, Papillary; D005260:Female; D006801:Humans; D008297:Male; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local; D011379:Prognosis; D012307:Risk Factors; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000473:pathology*