Visualization of lymphatic vascular invasion in breast cancer by multiphoton microscopy.

Lymphatic vascular invasion (LVI) is regarded as one of the independent factors which affect the prognosis of breast cancer. Once LVI is formed, it indicates the tumor has metastasized or has the possibility of metastasis. In this work, multiphoton microscopy (MPM), which relies on the two-photon excited fluorescence (TPEF) and second harmonic generation (SHG), was applied to identify the typical morphology of LVI and also visualize the histological features of LVI. Furthermore, the pixel density of collagen fibers was extracted as a quantitative parameter to differentiate LVI from the ductal carcinoma in situ (DCIS). By comparing with the corresponding H&E-stained images, it was confirmed that MPM can be used as an auxiliary tool for pathologists to diagnose LVI, and has a possibility for the application in clinical examination.