The Proportion of Malignancy in Incidental Thyroid Lesions on 18-FDG PET Study: A Systematic Review and Meta-analysis

Otolaryngol Head Neck Surg. 2014 Aug;151(2):190-200. doi: 10.1177/0194599814530861. Epub 2014 Apr 23.


Objective: To evaluate through a systematic review and meta-analysis the malignancy rates of thyroid incidentalomas identified in adults by 18-fluorodeoxyglucose positron emission tomography, computed tomography (18-FDG PET-CT) imaging studies.

Data sources: The literature search was conducted using OVID Medline, EMBASE, the Cochrane Library, Google Scholar, Pubmed, and reference list review (inception to April 2013) by 2 independent review authors.

Review methods: Studies with adults undergoing 18-FDG PET scan identifying a thyroid incidentaloma with definitive histological or cytological results reported were included.

Results: Thirty-one studies with a total of 197,296 PET studies and 3659 focal thyroid incidentalomas were identified with 1341 having definitive cytopathology or histopathology. The pooled proportion of malignancy was calculated as 19.8% (95% confidence interval [CI], 15.3%-24.7%) with 15.4% (95% CI, 11.4%-20.0%) of the total cases being papillary thyroid cancer. Distant metastases represented 1.1% (95% CI, 0.6%-1.8%) of the total cases.

Conclusions: Our systematic review and meta-analysis suggests that the incidence of malignancy is high in thyroid incidentalomas identified through 18-FDG PET imaging studies. Thyroid incidentalomas identified through 18-FDG PET require thorough investigation.

Keywords: incidental findings; papillary thyroid cancer; positron emission tomography; systematic review; thyroid.

Publication types

  • Meta-Analysis
  • Review
  • Systematic Review

MeSH terms

  • Fluorodeoxyglucose F18
  • Humans
  • Incidental Findings*
  • Positron-Emission Tomography*
  • Radiopharmaceuticals
  • Thyroid Gland / diagnostic imaging*
  • Thyroid Neoplasms / diagnostic imaging*


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18