Computer-aided Detection of Quantitative Signatures for Breast Fibroepithelial Tumors using Label-free Multi-Photon Imaging
Abstract Background Fibroadenomas (FAs) and phyllodes tumors (PTs) are major benign breast tumors. They are pathologically classified as fibroepithelial tumors, composed of a proliferation of both epithelial and stroma. Although the clinical management of PTs differs from FAs, distinction by core needle biopsy diagnoses is still challenging. Computer-aided diagnosis is playing a pivotal role in accurate and objective evaluation of medical images. This technology opens up a new route to a solution for diagnostic problems. Methods A combined technique of label-free imaging with multi-photon microscopy and artificial intelligence was applied to detect quantitative signatures that differentiate fibroepithelial lesions. Multi-photon excited autofluorescence and second harmonic generation (SHG) signals were detected in tissue sections. A pixel-wise semantic segmentation method using a deep learning framework was used to separate epithelial and stromal regions automatically. Quantitative signatures, the epithelial to stromal area ratio, and the collagen SHG signal strength were investigated for their ability to distinguish between FA and PT lesions. Results Multi-photon microscopy recordings of tissue sections revealed distinct morphology between the epithelia and stroma, and further indicated that stromal regions emit a strong SHG signal which derives from collagen fibrils. However, this signal strength differs between the lesions, suggesting differences of collagenous molecular composition between the two lesions. In order to investigate hypertrophy of the stroma and compare this to the epithelial areas, an image segmentation analysis with a pixel-wise semantic segmentation framework using a deep convolutional neural network was performed. The deep learning-based analysis showed accurate separation of epithelial and stromal regions. Further investigation was conducted to determine if scoring the epithelial to stromal area ratio could be a marker for differentiating fibroadenoma and phyllodes tissues; we determined that most samples can be clearly separated but some are difficult to separate by the signature. Further investigations on the collagen SHG signal strength within the stromal area revealed accurate classification of the breast tissue lesions. Conclusions Molecular and morphological changes detected through the assistance of computational and label-free multi-photon imaging techniques enabled us to propose quantitative signatures for epithelial and stromal alterations in breast tissues.