Optical coherence tomography (OCT) images. (A) OCT image of normal cervical tissue, showing a well-organized, three-layer architecture (optical structure) with sharp borders. The thin basement membrane (BM) could not be resolved by OCT. However, because the basement membrane separates the epithelium (EP) from stroma (ST), a sharp interface could be visualized (length of the white bar: 1 mm). (B) OCT image showing a cervical intraepithelial neoplasia (CIN-3) lesion. The intensity of the stromal layer increases with less-organized layer architecture. The stroma seemed to push its way towards the surface as vertical columns. (C) OCT image showing invasive carcinoma. The tissue surface is an unstructured homogeneous highly backscattering region with a complete lack of layer architecture (optical structure). The basement membrane is no longer intact or defined and the tissue microstructure is no longer organized. Reprinted with permission from Gallwas J, et al..