title: Thyroid Nodule Size at Ultrasound as a Predictor of Malignancy and Final Pathologic Size.
abstract: Thyroid-related mortality has remained constant despite the increasing incidence of thyroid carcinoma. Most thyroid nodules are benign; therefore, ultrasound and fine needle aspiration (FNA) are integral in cancer screening. We hypothesize that increased nodule size at ultrasound does not predict malignancy and correlation between nodule size at ultrasound and pathologic exam is good.
  
  
  
  Resected thyroids with preoperative ultrasounds were identified. Nodule size at ultrasound, FNA diagnosis by Bethesda category, size at pathologic examination, and final histologic diagnosis were recorded. Nodule characteristics at ultrasound and FNA diagnoses were correlated with gross characteristics and histologic diagnoses. Nodules for which correlation could not be established were excluded.
  
  
  
  Of 1003 nodules from 659 patients, 26% were malignant. Nodules <2 cm had the highest malignancy rate (∼30%). Risk was similar (∼20%) for nodules ≥2 cm. Of the 548 subject to FNA, 38% were malignant. Decreasing malignancy rates were observed with increasing size (57% for nodules <1 cm to 20% for nodules >6 cm). At ultrasound size cutoffs of 2, 3, 4, and 5 cm, smaller nodules had higher malignancy rates than larger nodules. Of the 455 not subject to FNA, 11% were malignant. Ultrasound size alone is a poor predictor of malignancy, but a relatively good predictor of final pathologic size (R2= 0.748), with less correlation at larger sizes. In nodules subject to FNA, false negative diagnoses were highest (6-8%) in nodules 3-6 cm, mostly due to encapsulated follicular variant of papillary carcinoma.
  
  
  
  Thyroid nodule size is inversely related to malignancy risk, as larger nodules have lower malignancy rates. However, the relationship of size to malignancy varies by FNA status. All nodules (regardless of FNA status) demonstrate a risk trough at ≥2 cm. Nodules subject to FNA show step-wise decline in malignancy rates by size, demonstrating that size alone should not be considered as an independent risk factor. Size at ultrasound shows relatively good correlation with final pathologic size. False negative rates are low in this series. Lesions with the appropriate constellation of clinical and radiographic findings should undergo FNA regardless of size. Both size and FNA diagnosis should influence the clinical decision-making process.
authors.affiliation: 1 Department of Pathology, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Allison
authors.initials: A
authors.lastname: Cavallo
authors.affiliation: 1 Department of Pathology, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Johnson
authors.affiliation: 2 Endocrine Surgery Research Program, Department of Surgery, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Michael G
authors.initials: MG
authors.lastname: White
authors.affiliation: 3 Pritzker School of Medicine, The University of Chicago , Chicago, Illinois.
authors.forename: Saaduddin
authors.initials: S
authors.lastname: Siddiqui
authors.affiliation: 1 Department of Pathology, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Antic
authors.affiliation: 4 Department of Radiology, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Melvy
authors.initials: M
authors.lastname: Mathew
authors.affiliation: 2 Endocrine Surgery Research Program, Department of Surgery, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Raymon H
authors.initials: RH
authors.lastname: Grogan
authors.affiliation: 2 Endocrine Surgery Research Program, Department of Surgery, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Peter
authors.initials: P
authors.lastname: Angelos
authors.affiliation: 2 Endocrine Surgery Research Program, Department of Surgery, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Edwin L
authors.initials: EL
authors.lastname: Kaplan
authors.affiliation: 1 Department of Pathology, The University of Chicago Medicine , Chicago, Illinois.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Cipriani
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D000066491:Clinical Decision-Making; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D016606:Thyroid Nodule / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013965:Thyroidectomy; D016896:Treatment Outcome; D014463:Ultrasonography
keywords: malignancy; pathologic size; thyroid nodules; ultrasound size