title: Incidental thyroid carcinoma by FDG-PET/CT: a study of clinicopathological characteristics.
abstract: BACKGROUND
  The rising incidence of incidental thyroid carcinoma (ITC) detected during fluoro-2-deoxy-D: -glucose (FDG)-positron emission tomography (PET)/computed tomography (CT) scanning poses a challenge to clinicians. The present study aims to critically evaluate the clinicopathological characteristics of ITC detected by FDG-PET/CT.
  
  
  METHODS
  Among the 557 patients managed at our institution, 40 (7.2%) patients were identified as having ITC. Of these, 22 patients had their tumor detected by FDG-PET/CT (PET group) and 11 by ultrasonography (USG group). Additional bedside ultrasonography ± fine-needle aspiration (FNA) was done in all patients at their clinic visit. The clinicopathological characteristics were compared between the PET and USG groups.
  
  
  RESULTS
  The PET group had significantly more patients with history of nonthyroidal malignancy (P < 0.001). Papillary carcinoma was the most common histological type in both groups. Despite having similar histological and prognostic features including tumor size, tumor multifocality, capsular invasion, extrathyroidal extension, and lymph node metastases, tumor bilaterality (or presence of contralateral tumor focus) was significantly more frequent in the PET than the USG group (P = 0.04). The tumors were also more advanced by the tumor-node-metastasis (TNM) staging system in the PET group (P = 0.021). None of the contralateral tumor foci were evident preoperatively. One patient in the USG group developed metastatic thyroid carcinoma in neck lymph nodes 28 months after thyroid resection.
  
  
  CONCLUSIONS
  ITC by FDG-PET/CT had higher incidence of tumor bilaterality than those detected by ultrasonography. Total thyroidectomy should be considered for ITC detected by FDG-PET/CT even for tumor size <10 mm.
authors.affiliation: Department of Surgery, University of Hong Kong, Hong Kong SAR, China.
authors.forename: T T
authors.initials: TT
authors.lastname: Law
authors.forename: Brian Hung-Hin
authors.initials: BH
authors.lastname: Lang
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000175:diagnosis* / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000175:diagnosis* / Q000601:surgery; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D015996:Survival Rate; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000601:surgery; D013965:Thyroidectomy; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18