Size of thyroid carcinoma by histotype and variants: A population-based study in a mildly iodine-deficient area.

ABSTRACT

BACKGROUND: Data relating the size of thyroid cancer with histological types and variants are scarce. METHODS: All incident thyroid cancer diagnosed between 2003 and 2012 in a mildly iodine-deficient area were derived from a population-based tumor registry. Undifferentiated/anaplastic thyroid cancer and incidental cases were excluded. Major diameter of thyroid cancer, as assessed by pathological examination, was stratified in classes ≤10 mm; 11-20 mm; 21-40 mm; and >40 mm. For each class, absolute and relative frequencies of histological types were calculated. RESULTS: Tumors >20 mm were more frequent among follicular thyroid carcinoma (FTC) and Hürthle cell carcinoma than in other histotypes, with median size of 22.50 mm (95% confidence interval [CI] 16.71-28.29) and 25.00 mm (95% CI 17.04-32.96) in FTC and Hürthle cell carcinoma, respectively. Odds ratio for tumors >20 mm was significant for FTC and Hürthle cell carcinoma only (P < .0001). CONCLUSION: Among the histotypes and variants of differentiated thyroid cancer, FTC and Hürthle cell carcinoma are characterized by the largest size.