To explore the expression and clinical significance of Toll-like receptor (TLR) 2 and TLR4 in non-puerperal mastitis (NPM) of different pathological types and clinical stages.

This was a retrospective analysis. The pathological sections from 141 patients with NPM and 10 patients with breast fibroma (control group) who underwent surgical treatment in the First Affiliated Huai’an Hospital of Nanjing Medical University from January 2012 to January 2017 were immunohistochemically detected. According to the postoperative pathological results, NPM patients was divided into granulomatous mastitis (GM, n=59), plasma cell mastitis (PCM, n=50) and other types of mastitis(n=32), and then the patients with GM or PCM were compared with patients with breast fibroma (control group). According to the clinical stage, 141 NPM patients were divided into acute stage (n=21), subacute stage (n=72) and chronic stage (n=48), which was compared with the control group, respectively. The expression levels of TLR2 and TLR4 in NPM of different pathological types and different clinical stages were determined, and then statistical analysis was carried out in combination with clinical data. The one-way analysis of variance was used to compare the expression levels of TLR2 and TLR4 among multiple groups. With heterogeneity of variance, the Tamhane’s method was used for pairwise comparison, otherwise, the LSD method was used for pairwise comparison. The clinical characteristics were compared between GM and PCM patients by χ² test.

The expression levels of TLR2 and TLR4 were 15.82 ± 4.96 and 27.27 ± 7.70 in the GM group, 15.29 ± 4.14 and 26.25 ± 6.63 in the PCM group, 6.12 ± 0.81 and 6.40 ±1.18 in the control group, respectively, indicating a significant difference among three groups (F= 21.613, 39.746, both P<0.001). The expression levels of TLR2 and TLR4 in the GM and PCM groups were significantly higher than those in the control group (all P<0.050). Moreover, the expression levels of TLR2 and TLR4 in NPM patients presented a significant difference among the acute phase, subacute phase, chronic phase groups and the control group (F=190.112, 246.965, both P<0.001). The expression levels of TLR2 and TLR4 in patients with acute NPM were 23.65 ± 2.32 and 40.10 ± 2.22, which were significantly higher than those in subacute NPM (12.35 ± 2.44 and 23.14 ± 4.56, both P<0.001), and those in chronic NPM (17.19± 2.36 and 29.36 ± 2.17, both P<0.001). GM patients had a significantly higher incidence of erythema nodosa in lower extremities compared with PCM patients [28.8% (17/59) vs 12.0% (6/50), χ² = 4.596, P=0.032].

TLR2 and TLR4 are highly expressed in acute NPM, and the TLR2/TLR4 signaling pathway may be involved in the occurrence and development of NPM. There is a significant difference in the incidence of erythema nodosa in lower extremities between GM and PCM patients.