Histological Analysis of γδ T Lymphocytes Infiltrating Human Triple-Negative Breast Carcinomas

Abstract

Breast cancer is the leading cause of cancer death in women and the second most common cancer worldwide after lung cancer. The remarkable heterogeneity of breast cancers influences numerous diagnostic, therapeutic, and prognostic factors. Triple-negative breast carcinomas (TNBCs) lack expression of HER2 and the estrogen and progesterone receptors and often contain lymphocytic infiltrates. Most of TNBCs are invasive ductal carcinomas (IDCs) with poor prognosis, whereas prognostically more favorable subtypes such as medullary breast carcinomas (MBCs) are somewhat less frequent. Infiltrating T-cells have been associated with an improved clinical outcome in TNBCs. The prognostic role of γδ T-cells within CD3(+) tumor-infiltrating T lymphocytes remains unclear. We analyzed 26 TNBCs, 14 IDCs, and 12 MBCs, using immunohistochemistry for the quantity and patterns of γδ T-cell infiltrates within the tumor microenvironment. In both types of TNBCs, we found higher numbers of γδ T-cells in comparison with normal breast tissues and fibroadenomas. The numbers of infiltrating γδ T-cells were higher in MBCs than in IDCs. γδ T-cells in MBCs were frequently located in direct contact with tumor cells, within the tumor and at its invasive border. In contrast, most γδ T-cells in IDCs were found in clusters within the tumor stroma. These findings could be associated with the fact that the patient's prognosis in MBCs is better than that in IDCs. Further studies to characterize these γδ T-cells at the molecular and functional level are in progress.

Keywords: breast cancer; histology; paraffin material; triple-negative breast cancer; γδ T-cells.

Figure 1

CD3⁺ and TCRγδ⁺ T-cells in normal breast tissue. Representative normal breast tissue stained for CD3⁺ (A) and TCRγδ⁺ (B) T-cells. Controls included a TCRγδ⁺ T-cell lymphoma involving the stomach (C). CD3⁺ cells are detected by the brown chromogen (A) while TCRγδ⁺ cells are stained red (B,C).

Figure 2

TCRγδ⁺ T-cells in representative triple negative invasive ductal carcinomas (IDCs) and medullary breast carcinomas (MBCs). Two representative cases of IDC (A,B) and MBC (C,D) were stained by IHC for TCRγδ⁺ T-cells. The tumor area is marked with T, TCRγδ⁺ T-cells are detected by the red chromogen. The tumor area is marked (“T”).

Figure 3

CD3⁺ and TCRγδ⁺ T-cells in an invasive ductal carcinoma (IDC). IHC of an IDC with a rich lymphocytic infiltration that extends into the tumor parenchyma (T). CD3⁺ T-cells are detected by the brown chromogen (A) while TCRγδ⁺ cells are stained red (B). The tumor area is marked (“T”).

Figure 4

TCRγδ⁺ T-cells in benign proliferative breast disease. TCRγδ IHC in two representative fibroadenomas (from seven cases analyzed). Fibrotic tissue (“F”) and normal breast tissue (“N”) are marked. There is a small lymphocytic infiltrate with very few TCRγδ⁺ cells.

Figure 5

Apoptotic tumor cells in triple negative IDC and MBC. Cleaved-caspase-3⁺ tumor cells are detected in a representative case of IDC and MBC by a dark blue chromogen within the tumor area.