Expression of T cell-related proteins in breast ductal carcinoma <i>in situ</i>.

This study aims to explore the expression of T cell subtype markers within the immune cells constituting the tumor microenvironment of ductal carcinoma <i>in situ</i> (DCIS) and to assess its implications. A tissue microarray comprising 191 cases of breast DCIS was created, and immunohistochemistry staining for T cell subtype markers (STAT3, STAT4, STAT-6, and FOXP3) was conducted. The DCIS cases were categorized into luminal, HER-2, and TNBC (Triple-negative breast cancer) types based on ER, PR, HER-2, and Ki-67 results. Additionally, they were classified as low-TIL (tumor-infiltrating lymphocytes) (<10%) or high-TIL (≥10%) types according to stromal TIL. Results revealed that 54.6% were luminal, 39.5% HER-2, and 5.9% TNBC. STAT3 exhibited a high positivity rate in luminal-type tumor cells, while STAT3, STAT4, STAT6, and FOXP3 showed elevated positivity rates in TNBC immune cells (<i>p</i><0.05). Furthermore, a higher positivity rate was observed in high-TIL immune cells compared with low-TIL (<i>p</i><0.001). The strongest agreement between T cell subtype markers in immune cells was found between STAT3 and STAT4 (OA=83.7%, κ=0.658), whereas the lowest was between STAT4 and FOXP3 (OA=71.7%, κ=0.370). In immune cells, STAT3 and STAT4 positivity correlated with necrosis (<i>p</i><0.001), and the absence of positivity in all immune cell-related proteins in DCIS with necrosis was associated with poor prognosis (<i>p</i>=0.013). In conclusion, the immune cells in DCIS exhibit positivity for diverse T cell subtype markers, with TNBC and high-TIL DCIS displaying heightened positivity.