Podoba, Jan1; Grigerová, Marianna1; Mojtová, Emília1; Griger, Martin1
1 Department of Endocrinology, Slovak Medical University and St. Elizabeth Cancer Institute, Bratislava, Slovakia
Background: Coexistence of autoimmune thyroiditis (AIT) and papillary thyroid cancer (PTC) has been well documented, but causality is still a matter of debate.
Purpose: to find out: 1/ the incidence of AIT in differentiated thyroid cancer (DTC) patients, 2/ the clinical course of PTC associated with AIT, 3/ the relationship between AIT and PTC.
Methods: Histological and laboratory results of 1,352 DTC patients seen during the period of 2005-2014 were reviewed. Diagnosis of AIT was based on histology and/or high anti-TPO levels (3-times above upper reference range limit).
Results: The ratio of AIT in DTC patients was 552 out of 1,352 (40.8%). In 362 of them AIT was known before the diagnosis of DTC. After subtracting this group from the total number of DTC patients the incidence of AIT decreased but still prevailed relatively high – 19.2%. The ratio of AIT in DTC patients did not increase with age. Among DTCs associated with AIT the ratio of PTC was 95%.In comparison with PTCs without AIT, PTCs coexisting with AIT had better initial prognostic indicators, e.g. significantly higher incidence of small cancers (and microcarcinomas) and lower incidence of distant metastases. When we compared prognostic indicators of PTCs without AIT to those where AIT was revealed only after surgery no significant differences were found. AIT does not improve the clinical course of PTC patients.
Conclusion: With regard to its high incidence among PTC patients, AIT might belong to predisposing factors of PTC. AIT is not a protective factor against progression of PTC.