Dear Editor,

We read with interest the article “The clinicopathologic differences in papillary thyroid carcinoma with or without co-existing chronic lymphocytic thyroiditis” by Yoon et al. [1] because it reinforces our previous results and new data in a large Brazilian population of patients with differentiated thyroid carcinoma (DTC) [2]. In a retrospective analysis comparing 195 patients with papillary thyroid carcinoma (PTC), Yoon et al. showed that patients presenting concurrent chronic lymphocytic thyroiditis (CLT) had less aggressive tumors. We totally agree with this statement.

Interestingly, 56 out of 195 (28.7%) patients with PTC, enrolled in the study by Yoon et al., presented concurrent CLT. In our cohort, 84 out of 266 (31.58%) DTC patients presented concurrent CLT, suggesting a similar incidence of concurrent CLT in Korean and Brazilian populations.

Yoon and col. showed that concurrent CLT was more common in women. In addition, patients with concurrent CLT were younger than those patients without CLT. Concurrent CLT was correlated with small tumor size and absence of capsular invasion. Furthermore, the rate of central lymph node (CLN) metastasis was higher in patients without CLT than patients with CLT. In our cohort, the presence of concurrent HT was also significantly correlated with favorable prognostic features including female gender (p = 0.0274), no extrathyroidal tumor invasion (p = 0.0028), absence of metastasis at diagnosis (p = 0.0026), and small tumors (p = 0.0110), thus confirming the tight relationship between concurrent autoimmunity and histopathological features of low aggressiveness.

Unfortunately, since short follow-up was accessed, Yoon et al. did not study patient outcome according to presence/absence of concurrent CLT. Using the same criteria introduced by Huang et al. [3] to define recurrence, metastasis and disease-free survival, a log-rank test also confirmed that the absence of concurrent CLT was more frequent in our patients who had recurrences (p = 0.0015), suggesting that autoimmune activity against the gland may exert a protective effect on the outcome of DTC patients [2]. In fact, we recently demonstrated that concurrent CLT was accompanied by a mixture of intratumoral lymphocytic infiltrates, revealing a putative antitumor immune response (article submitted).

However, it is worthy of note that our results demonstrated that even the presence of concomitant CLT is not enough to modify the mortality rate of DTC patients, suggesting that an appropriate management of DTC patient is in fact the most important modifiable prognostic factor.

Sincerely,

Lucas Leite Cunha and Laura Sterian Ward