title: Is an Increase in Thyroid Nodule Volume a Risk Factor for Malignancy?
abstract: BACKGROUND
  Most benign thyroid nodules found on fine-needle aspiration cytology (FNAC) can be followed with periodic ultrasonography. During follow-up, when nodules grow, re-aspiration or surgical resection for a histologic diagnosis is recommended. However, there is little evidence regarding the malignancy risk associated with nodule growth.
  
  
  METHODS
  We retrospectively reviewed the records of 542 patients with FNAC-diagnosed adenomatous nodules (ANs) who underwent surgery in 2011-2012 at Kuma Hospital. Among them, 196 patients had surgical resection because of nodule volume growth (median, 1.94 times; range, 1.21-27.60) during the observation period (mean, 45.9 months). Excluding nodule growth, the remaining 346 patients underwent surgery for various reasons including the large size of nodules or the appearance of undefined ultrasound features suspicious for malignancy during follow-up. For comparison, we reviewed 409 patients with FNAC-diagnosed follicular neoplasms (FNs) operated on in 2011-2013. Most (n=327) underwent surgery shortly after the FNAC diagnosis, while 82 patients were observed for a period of time and had a late operation due to nodule volume growth (median, 2.70 times; range, 1.27-15.82).
  
  
  RESULTS
  The histologic diagnoses of the 196 growing FNAC-diagnosed ANs were 158 ANs, 32 follicular adenomas (FAs), 4 follicular tumors of uncertain malignant potential (FT-UMP; 2%), and 2 malignancies (1%). The 346 patients who underwent surgery for reasons other than nodular growth had 16 FT-UMP (4.6%) and 16 malignancies (4.6%). This suggests that nodule growth itself is not a risk factor for malignancy. On the other hand, there were 23 FT-UMP (28%) and 15 malignancies (18.3%) in the 82 growing FNAC-diagnosed FNs, while 44 FT-UMP (13.5%) and 54 malignancies (16.5%) in the 327 FNAC-diagnosed FN patients who underwent immediate surgery. The malignant potential was significantly higher in the growing-FN group than the immediate-surgery FN group (p<0.05). No significant difference was found in the volume change between the benign and the FT-UMP plus malignant group in the growing FNs, suggesting that a growth rate does not correlate with malignant potential.
  
  
  CONCLUSIONS
  This is the first demonstration that the malignancy risk is low in FNAC-diagnosed ANs, even if the nodules grow significantly, whereas FNs have a higher risk when they grow.
authors: 1 Department of Medicine, Kuma Hospital , Kobe, Japan .
authors: Hirotoshi
authors: H
authors: Nakamura
authors: 2 Department of Pathology, Kuma Hospital , Kobe, Japan .
authors: Mitsuyoshi
authors: M
authors: Hirokawa
authors: 3 Department of Laboratory, Kuma Hospital , Kobe, Japan .
authors: Hisashi
authors: H
authors: Ota
authors: 4 Department of Surgery, Kuma Hospital , Kobe, Japan .
authors: Minoru
authors: M
authors: Kihara
authors: 4 Department of Surgery, Kuma Hospital , Kobe, Japan .
authors: Akihiro
authors: A
authors: Miya
authors: 4 Department of Surgery, Kuma Hospital , Kobe, Japan .
authors: Akira
authors: A
authors: Miyauchi
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D000236:Adenoma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle; D002277:Carcinoma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D002291:Carcinoma, Papillary; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D016606:Thyroid Nodule / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D013965:Thyroidectomy; D047368:Tumor Burden; D014463:Ultrasonography