Label-free multiphoton imaging to identify two types of tumor-infiltrating lymphocytes in breast tumor microenvironment

Breast tumor microenvironment is composed of tumor cells, tumor-related cells, blood vessels and a series of extracellular matrix fibers. Tumor-infiltrating lymphocytes (Tils) in the microenvironment can directly or indirectly influence other components in the microenvironment, thus promoting the occurrence and development of tumors. Multiphoton microscopy (MPM) is based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG). And it does not require the use of exogenous probes or staining of tissue. In this study, large-size images with subcellular resolution of the breast tumor tissue was performed using MPM. The results showed that the MPM could clearly distinguish intraepithelial Tils (iTils) and stromal compartments Tils (sTils) by comparing the signal strength and morphological difference. It demonstrated that MPM could be used as a means of pathological diagnosis and in clinical application.