title: Positron emission tomography-positive thyroid nodules: rate of malignancy and histological features.
abstract: BACKGROUND
  Thyroid nodules may be incidentally detected on (18) F-FDG-positron emission tomography (PET) scans. Previous reports suggest a high incidence of malignancy in FDG-avid nodules. The aims of this study were to examine the incidence of malignancy in a large cohort and to report on the histological features. The findings suggest that poor prognostic histologic features are often associated with FDG-avid thyroid nodules and this may have clinical implications.
  
  
  METHODS
  A retrospective review of prospectively collected data was conducted. A database containing all patients who underwent PET scanning at a single tertiary referral centre from January 2006 to January 2013 was searched to identify those with incidental PET-positive thyroid nodules. Patients with known preexisting thyroid disease were excluded from analysis. The demographics, fine-needle aspiration (FNA) biopsy result and operative histopathology were analysed.
  
  
  RESULTS
  A total of 27 851 FDG-PET scans were performed of which 221 found incidental PET-positive thyroid nodules (incidence 0.8%). Fifty-three patients went on to have further investigation and 21 of these were found to have malignant disease (incidence 39.6%). Histopathological examination of 12 malignant nodules revealed an expected rate of poor prognostic features, including poorly differentiated subtype (8.3%), lymphovascular invasion (16.7%), perineural invasion (8.3%) and extrathyroid extension (33.3%).
  
  
  CONCLUSIONS
  Our data indicate that PET-positive thyroid nodules are associated with a high incidence of malignancy. This finding provides strong support for further investigation including FNA biopsy in all surgically suitable patients.
authors.affiliation: Department of Otolaryngology, Fremantle Hospital, Fremantle, Western Australia, Australia.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Flukes
authors.affiliation: Department of Nuclear Medicine, Fremantle Hospital, Fremantle, Western Australia, Australia.
authors.forename: Nat
authors.initials: N
authors.lastname: Lenzo
authors.affiliation: Department of Nuclear Medicine, Fremantle Hospital, Fremantle, Western Australia, Australia.
authors.forename: Girolamo
authors.initials: G
authors.lastname: Moschilla
authors.affiliation: Department of Otolaryngology, Fremantle Hospital, Fremantle, Western Australia, Australia.
authors.forename: Chady
authors.initials: C
authors.lastname: Sader
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle / Q000379:methods; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D013964:Thyroid Neoplasms / Q000175:diagnosis*; D016606:Thyroid Nodule / Q000175:diagnosis*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: biopsy; fine-needle; histology; positron emission tomography; thyroid carcinoma; thyroid nodule