title: Thyroid incidentalomas discovered on positron emission tomography CT scanning - Malignancy rate and significance of standardised uptake values.
abstract: OBJECTIVE
  Increasing use of 18F-Fluorodeoxy glucose (FDG) Positron Emission Tomography Computed Tomography (PET CT) has resulted in an increased frequency of incidentally discovered areas of focally increased FDG uptake within the thyroid gland - thyroid incidentalomas. We aimed to compare radiological characteristics of thyroid incidentalomas with cytology, histology and ultrasound findings.
  
  
  METHODS
  We examined all FDG PET CT scan reports for all patients undergoing this investigation over a 6 year period in a single tertiary cancer centre. All PET CT scans followed an agreed proforma allowing reports mentioning "thyroid" to be identified. Reports commenting on a positive finding within the thyroid gland were investigated further manually. Incidental mentions of thyroid with no underlying abnormality were discounted from analysis.
  
  
  RESULTS
  In the study period, 7221 patients underwent FDG PET CT scanning in our unit. Within this group 75 (1%) showed diffuse FDG uptake and 81 (1.1%) showed focal uptake (thyroid incidentalomas). Only 30 patients (37%) with incidentalomas had further investigation and malignancy rate was 23% (7/30). Median Standardised Uptake Values (SUV) in malignant lesions was 9.9 (range 3.5-17.8) whilst in benign lesions and diffuse lesions it was 5.4 (2.8-32) and 4.2 (2.1-25.6) respectively (p = 0.0013, Kruskal Wallis).
  
  
  CONCLUSIONS
  There remains a need to develop a standardised approach to the investigation and management of thyroid incidentalomas discovered on FDG PET CT scanning. Up to 1 in 4 of these patients will harbour thyroid malignancy.
authors.affiliation: North West Deanery, Manchester, UK.
authors.forename: R
authors.initials: R
authors.lastname: Brindle
authors.affiliation: The Christie NHS Foundation Trust, 550 Wilmslow Rd, Manchester, M20 4BX, UK.
authors.forename: D
authors.initials: D
authors.lastname: Mullan
authors.affiliation: The Christie NHS Foundation Trust, 550 Wilmslow Rd, Manchester, M20 4BX, UK.
authors.forename: B K
authors.initials: BK
authors.lastname: Yap
authors.affiliation: University of Manchester, Manchester Academic Health Sciences Centre, University Hospital of South Manchester, Southmoor Road, Manchester, M23 9LT, UK. Electronic address: ashu.gandhi@uhsm.nhs.uk.
authors.forename: A
authors.initials: A
authors.lastname: Gandhi
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging* / Q000473:pathology; D000368:Aged; D002277:Carcinoma / Q000000981:diagnostic imaging* / Q000473:pathology; D002291:Carcinoma, Papillary; D015331:Cohort Studies; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D033162:Incidental Findings; D008223:Lymphoma / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D000077273:Thyroid Cancer, Papillary; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000473:pathology; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18F-fluorodeoxy glucose (FDG) positron emission tomography computed tomography; Standardised uptake values; Thyroid cancer; Thyroid incidentaloma