Decreased staging of differentiated thyroid cancer in patients with chronic lymphocytic thyroiditis

PURPOSE: The biological association between chronic lymphocytic thyroiditis (CLT) and differentiated thyroid cancer (DTC) has not been elucidated yet. The aim of the study was to assess whether the presence of CLT exerts any influence on clinical or histological presentation of DTC. METHODS: Nine hundred and seven consecutive patients with DTC treated in the years 1998–2016 were divided into two groups according to the presence or absence of concomitant CLT. The statistical differences were analysed. RESULTS: Out of 907 patients included in the study, 331 were diagnosed with DTC and CLT (studied group), while 576 patients with DTC but without CLT constituted a control group. The distribution of papillary and follicular thyroid cancer did not differ. In CLT group, the prevalence of pT1 was greater than for pT2–pT4 DTC (P = 0.0003; OR = 1.69, 95% CI 1.27–2.24) compared to controls (68.3 vs. 56.1%, respectively). The presence of multifocal lesions was similar. The thyroid capsule infiltration without extrathyroidal invasion (P < 0.0001; OR = 0.21, 95% CI 0.14–0.31) was more frequent in the studied group, unlike extracapsular invasion, which was significantly more often present in patients with DTC but without CLT (P = 0.004; OR = 1.66; 95% CI 1.17–2.34) as well as nodal involvement (P = 0.048; OR = 0.65, 95% CI 0.42–0.99). CONCLUSIONS: The collected data indicate a protective role of CLT in preventing the spread of the DTC. The presence of CLT might limit tumour growth to the primary site.