title: Coexistent thyroiditis is associated with lower tumour stage in thyroid carcinoma.
abstract: BACKGROUND
  Microsatellite instability (MSI) is a new mechanism described in carcinogenesis of several tumours and seems to predispose for cancer in some chronic inflammatory diseases. As thyroiditis is thought to be both the cause and the consequence of thyroid carcinoma, it was the aim of this retrospective study to investigate the epidemiology and the influence of a coexistent thyroiditis on prognosis and clinicopathological parameters in an iodine-deficient area.
  
  
  METHODS
  The grade of lymphocytic infiltration (LI) of 153 thyroid carcinomas was determined in paraffin-embedded tissues: G0 = no LI, G1 = peritumoral LI, G2 = peritumoral LI with follicle, G3 = diffuse LI. A non-radioactive PCR-based screening method was used for detection of MSI.
  
  
  RESULTS
  Twenty-seven (17.7%) out of 153 carcinomas were accompanied by thyroiditis (G1, 16; G2, 5; G3, 6). Ten cases fulfilled the criteria necessary for diagnosing Hashimoto's thyroiditis. Nine out of 10 (90%) Hashimoto's cases and 16 out of 17 (94%) other thyroiditis cases were associated with a significantly (chi2 < 0.01) lower pT stage (pT1, pT2) than cases without thyroiditis. No statistical association was found by comparing multifocality or sclerosing variants with the grade of lymphocytic infiltration. MSI was detected neither in patients with severe inflammation nor in the absence of thyroiditis.
  
  
  CONCLUSIONS
  MSI does not seem to play a role in the pathogenesis of thyroid carcinoma. Coexistent thyroiditis is associated with a lower pT stage and thus could be an indicator of a better prognosis.
authors.affiliation: University of Regensburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schäffler
authors.forename: K D
authors.initials: KD
authors.lastname: Palitzsch
authors.forename: C
authors.initials: C
authors.lastname: Seiffarth
authors.forename: H M
authors.initials: HM
authors.lastname: Höhne
authors.forename: F J
authors.initials: FJ
authors.lastname: Riedhammer
authors.forename: F
authors.initials: F
authors.lastname: Hofstädter
authors.forename: J
authors.initials: J
authors.lastname: Schölmerich
authors.forename: J
authors.initials: J
authors.lastname: Rüschoff
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007455:Iodine / Q000172:deficiency; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000150:complications* / Q000235:genetics / Q000473:pathology; D013966:Thyroiditis / Q000150:complications* / Q000235:genetics
chemical_list: D007455:Iodine