title: Impact of Hashimoto's thyroiditis, TSH levels, and anti-thyroid antibody positivity on differentiated thyroid carcinoma incidence.
abstract: BACKGROUND
  The relationship between Hashimoto's thyroiditis (HT) and thyroid cancer (TC) is controversial. While most surgical studies report a high incidence of malignancy among patients with HT, cytological studies do not. The role of autoantibodies in the incidence of malignancy is unclear.
  
  
  METHODS
  A single-centre retrospective observational study was conducted in patients evaluated for thyroid nodules by US-guided fine-needle aspiration cytology (FNAC) and, if indicated, by surgery. The levels of thyroid-stimulating hormone (TSH) and anti-thyroid antibodies were measured at the time of FNAC.
  
  
  RESULTS
  Of 4947 patients, 599 (12.1%) were diagnosed with HT. A malignant/suspicious cytological result was found in 14.2% of the patients with HT and in 15.2% of the others. The odds ratio (OR) for malignancy in HT was 0.921 (0.716-1.183, p = 0.51). Of 1603 patients who underwent surgery, differentiated thyroid carcinoma was found in 29.5% of the HT patients and in 15.2% of the others (OR 2.33, 95% confidence interval CI, 1.403-3.854, p < 0,001). Low TSH (< 0.4 mIU/L) decreased the malignancy rate in the entire patient population, both when considering the cytological results and the surgical results. This was not confirmed in the subgroup diagnosed with HT. No relationship was observed between autoantibodies against thyroid peroxidase (ATP) or thyroglobulin (ATG) and malignancy rate.
  
  
  CONCLUSIONS
  No association between HT and thyroid cancer was observed cytologically; a positive relationship in histological series was caused by selection bias. Low TSH levels decreased the risk of TC in patients with nodular goitre, but this has not been proven in patients with HT.
authors.affiliation: University Hospital in Hradec Kralove, 4th Dept. of Internal Medicine and Charles University, Faculty of Medicine in Hradec Kralove, Hradec Kralove, Czech Republic. filip.gabalec@gmail.com.
authors.forename: Filip
authors.initials: F
authors.lastname: Gabalec
authors.forename: Libuse
authors.initials: L
authors.lastname: Srbova
authors.forename: Marketa
authors.initials: M
authors.lastname: Nova
authors.forename: Eva
authors.initials: E
authors.lastname: Hovorkova
authors.forename: Helena
authors.initials: H
authors.lastname: Hornychova
authors.forename: Iva
authors.initials: I
authors.lastname: Jakubikova
authors.forename: Ales
authors.initials: A
authors.lastname: Ryska
authors.forename: Jan
authors.initials: J
authors.lastname: Cap
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000276:immunology; D005260:Female; D050031:Hashimoto Disease; D006801:Humans; D015994:Incidence; D007453:Iodide Peroxidase / Q000276:immunology; D033862:Iron-Binding Proteins / Q000276:immunology; D008297:Male; D012189:Retrospective Studies; D013954:Thyroglobulin / Q000276:immunology; D013961:Thyroid Gland / Q000276:immunology / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000097:blood / Q000453:epidemiology*; D013972:Thyrotropin / Q000097:blood*
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D033862:Iron-Binding Proteins; D013972:Thyrotropin; D013954:Thyroglobulin; C056658:TPO protein, human; D007453:Iodide Peroxidase
keywords: biopsy; fine-needle biopsy; thyroid cancer; thyroid nodule; thyroiditis