No considerable changes in papillary thyroid microcarcinoma characteristics over a 30-year time period.

Background: The prevalence of papillary thyroid microcarcinoma (PTMC) is continuously increasing but its clinical significance and management is still debatable. The aim of this study was to investigate possible changes in the clinical presentation, tumor characteristics, treatment modalities and long-term outcome during the last three decades in patients with PTMC.

Methods: We studied 335 patients with PTMC who were followed up for at least 5 years, from 1982 to 2015, and treated in accordance with the current literature or guidelines at each time-period. Patients were classified according to year of diagnosis into two time periods, TP1 from 1982-2000 and TP2 from 2001-2010.

Results: The mean follow-up of the whole cohort was 10.6 ± 5.3 (median 9) years. No change was noted in the mean age at diagnosis or the female to male ratio during the two time periods. In regard to tumor characteristics, multifocality and non-encapsulated follicular variant of PTMC was more often present while classic PTMC was less common in patients in the TP2, compared to patients in the TP1 (p = 0.007, p < 0.001 and p = 0.043 respectively). The prevalence of incidental PTMC was high but similar in both time periods (84.6 vs 80 %, p = 0.286). The majority of patients in TP2 underwent a total or near total thyroidectomy compared to patients in TP1 (91.7 vs 80 %, p = 0.001). However, more patients underwent thyroidectomy for toxic multinodular disease and less for Graves' disease during TP1 compared to patients in the TP2 (p = 0.02 and 0.043 respectively). A significant percentage of patients underwent adjuvant radioiodine ablation, yet no difference was found between the two time periods (73.8 vs 79.5 %, p = 0.228). The rate of persistence was very low and not significant (3.1 vs 6.6 %, p = 0.165), while disease recurrence was observed in only 2 (0.6 %) patients, one from each time period.

Conclusions: We did not observe any important changes regarding the clinical presentation or tumor characteristics of PTMCs during a 30-year period. With applied interventions a favorable course was confirmed in the majority of patients without differences in recurrence or persistence during the last three decades.