Abstract
Although some studies have investigated the clinicopathologic relationships between papillary thyroid carcinoma (PTC) and Hashimoto's thyroiditis (HT), there is still no clear understanding of differences in tumor immune microenvironment for PTC with coexisting HT and HT effect on PTC progression. The aim of this study was to clarify immune-mediated mechanisms of coexisting HT, which might influence PTC progression. 30 patients with histologically confirmed conventional-type PTC and 30 patients with PTC and coexisting HT were enrolled in the study. To analyze the role of immune-mediated links between PTC and HT, immunohistochemical investigation was conducted to count the number of different immune cells including T-cytotoxic cells (CD8), plasma cells (CD138), Treg cells (FOXP3), mast cells (MCT), and M2 macrophages (CD163). It was shown that despite the high number of immune cells in the intact thyroid tissues of PTC patients with coexisting HT there were no significant differences in M2 macrophages, mast cells and Treg counts inside PTC with or without HT. PTC with HT was associated with a higher number of CD8+ cells (P < 0.001) reflecting the ability of immune system to generate and recruit T-cytotoxic cells in tumor area, which can explain the protective effect of HT on PTC progression. Lymph node metastases development was associated with an increased number of mast cells, M2 macrophages and Treg along with a decreased plasma cells count regardless of coexisting HT. However, we did not find significant differences in T-cytotoxic cells quantity in node-positive and node-negative patients with or without HT, which encourages further investigation of immune escape mechanisms in PTC.
Highlights
Worldwide, an increase in the incidence of papillary thyroid cancer (PTC) has been reported
When assessing immune cells number in PTC tumors in patients with and without lymph node metastases (LNM) (Table 4), we found out that LNM development was associated with an increased number of myeloid cells
PTC development is accompanied by immune cells recruitment and infiltration of tumor area by a high number of innate (M2 macrophages and mast cells) and adaptive immunity cells
Summary
An increase in the incidence of papillary thyroid cancer (PTC) has been reported. A link between cancer and inflammation is well-established but still debatable for inflammatory thyroid diseases and PTC (Galdiero et al, 2016; Paparodis et al, 2014). The most common inflammatory thyroid disease is Hashimoto's thyroiditis (HT), known as chronic lymphocytic or autoimmune thyroiditis (Kim et al, 2009). The connection between HT and PTC was first described in 1955 (Dailey et al, 1955), and since numerous epidemiological studies have confirmed high coexistence between HT and PTC ranging from 20% to 85% (Konturek et al, 2013; Lee et al, 2013). There is confirmed connection between HT and PTC, different studies have not found the link between HT and other thyroid cancers including follicular, medullary, or anaplastic variants (de Paiva et al, 2017)
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