title: Lymphocytic thyroiditis on histology correlates with serum thyroglobulin autoantibodies in patients with papillary thyroid carcinoma: impact on detection of serum thyroglobulin.
abstract: BACKGROUND
  Serum thyroglobulin (Tg), the marker of residual tumor in papillary thyroid carcinoma, can be underestimated in patients with Tg autoantibodies (TgAb). TgAb are due to a coexistent lymphocytic thyroiditis (LT) or the papillary thyroid carcinoma per se. TgAb assays are highly discordant.
  
  
  METHODS
  We evaluated 141 patients with a clinical diagnosis of nodular thyroid disease, 32 of Hashimoto's thyroiditis, and four of Graves' disease, who underwent total thyroidectomy for an associated papillary thyroid carcinoma. Patients were classified as papillary thyroid carcinoma-lymphocytic thyroiditis (PTC-T) and papillary thyroid carcinoma (PTC) according to the presence or absence of LT on histology. Tg was measured before thyroid remnant ablation, when it is expectedly detectable, by an immunometric assay (IMA) and TgAb by three noncompetitive IMA and three competitive radioimmunoassays (RIA). The number of lymphocytes was compared with TgAb concentration.
  
  
  RESULTS
  Seventy-two of 177 patients (40.7%) were classified as PTC-T and 105 (59.3%) as PTC. Although the tumor stage was similar in the two groups, Tg was undetectable in more PTC-T (37 of 72) than PTC (12 of 105) (P < 0.01), and Tg values were lower in the former (0; 0-4.7 ng/ml) (median; 25th to 75th percentiles) than in the latter group (9.7; 2.7-24.2) (P < 0.01). Accordingly, the percent of positive TgAb by the six assays resulted in higher PTC-T (29.2-50.0%) than PTC (1.9-6.7%) (P < 0.01). Among 49 patients with undetectable Tg, TgAb were more frequently positive by IMA (57.1-63.3%) than RIA (30.6-42.9%). The number of lymphocytes correlated with TgAb concentration in all six assays (0.34 < Rho < 0.46) (all P < 0.01).
  
  
  CONCLUSIONS
  In papillary thyroid carcinoma, LT on histology must be carefully searched for because it is frequently associated with TgAb and therefore mistakenly low or undetectable Tg. TgAb can be missed by some assays. In absence of LT, TgAb are rare.
authors.affiliation: Department of Endocrinology, University Hospital of Pisa, Via Cisanello 2, 56124, Pisa, Italy. latrofaf@libero.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Latrofa
authors.forename: Debora
authors.initials: D
authors.lastname: Ricci
authors.forename: Lucia
authors.initials: L
authors.lastname: Montanelli
authors.forename: Roberto
authors.initials: R
authors.lastname: Rocchi
authors.forename: Paolo
authors.initials: P
authors.lastname: Piaggi
authors.forename: Eleonora
authors.initials: E
authors.lastname: Sisti
authors.forename: Lucia
authors.initials: L
authors.lastname: Grasso
authors.forename: Fulvio
authors.initials: F
authors.lastname: Basolo
authors.forename: Clara
authors.initials: C
authors.lastname: Ugolini
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D044963:Biopsy, Fine-Needle / Q000379:methods; D001774:Blood Chemical Analysis / Q000379:methods; D002277:Carcinoma; D002291:Carcinoma, Papillary; D003584:Cytological Techniques; D003940:Diagnostic Techniques, Endocrine; D005260:Female; D006801:Humans; D017254:Leukemic Infiltration / Q000175:diagnosis / Q000453:epidemiology / Q000473:pathology; D008214:Lymphocytes / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D013954:Thyroglobulin / Q000032:analysis / Q000097:blood* / Q000276:immunology; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology; D013967:Thyroiditis, Autoimmune / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology / Q000473:pathology*
chemical_list: D001323:Autoantibodies; D013954:Thyroglobulin