Chronic lymphocytic thyroiditis protects against recurrence in patients with cN0 papillary thyroid cancer.

BACKGROUND

Chronic lymphocytic thyroiditis (CLT) frequently coexists with papillary thyroid carcinoma (PTC) that exhibits normal thyroid function. However, few studies have investigated the relationship between CLT and clinically lymph node (LN)-negative PTC. The aim of this study was to evaluate the relationship between subclinical central LN metastasis and CLT, and to assess the impact of CLT on the recurrence of clinically LN-negative PTC.

METHODS

We investigated the medical records of 850 patients with PTC who underwent prophylactic bilateral central neck dissection as well as total thyroidectomy between 2004 and 2010; the median follow-up time was 95.5 months (range, 12-158 months).

RESULTS

CLT was observed in 480 patients (56.5%). Female sex, a preoperative thyroid-stimulating hormone level >2.5 mU/L, a primary tumor ≤1 cm, no gross extrathyroidal extension, high number of harvested LNs, low number of metastatic LNs, and positive anti-thyroglobulin (Tg) antibody at 1 year post-initial treatment were significantly associated with the presence of CLT. Multivariate analysis revealed that patients with N1a stage (vs. N0 stage; hazard ratio [HR], 3.255; 95% confidence interval [CI], 1.290-8.213; p = 0.012) and positive anti-Tg antibody at 1 year post-initial treatment (vs. negative anti-Tg antibody; HR, 5.118; 95% CI, 2.130-12.296; p < 0.001) had poorer recurrence-free survival (RFS), while those with CLT (vs. no CLT; HR, 0.357; 95% CI, 0.157-0.812; p = 0.014) had favorable RFS outcomes.

CONCLUSIONS

CLT is associated with less aggressive tumor characteristics and LN metastasis. Clinically LN-negative PTC patients with CLT experience longer RFS intervals than those without CLT.