In Vivo Noninvasive Imaging of Healthy Lower Lip Mucosa: A Correlation Study between High-Definition Optical Coherence Tomography, Reflectance Confocal Microscopy, and Histology

Table 3

Reflectance confocal microscopy, high-definition optical coherence tomography, and conventional histology morphological characteristics in lip mucosa according to tissue depth.

Reference mark	Depth	RCM characteristics	HD-OCT “en-face” characteristics	Histology
Z0	0 𝜇m	Highly scattering homogenous	Highly scattering homogenous layer	Nonhomogenously parakeratinized
Z1	4.96 𝜇m	Cytoplasmic granular appearance	Granular appearance and high scattering	Wanting granular layer. Cells appear very eosinophilic, thin and flat. Narrow intercellular spaces
Z2	29.79 𝜇m	Cytoplasmic border becomes apparent	Cytoplasmic granular appearance and areas with honeycomb pattern	Cells and nuclei become flat and irregularly shaped. Nuclei acquire pyknotic appearance
Z3	84.36 𝜇m	Wider honeycomb pattern. May be difficult to clearly distinguish nuclei. Dermal papillae may start becoming visible	Dermal papillae may start becoming visible	In the prickle layer, cells appear round or polygonal. Nuclei seem intensely basophilic and centrally located
Z4	124.00 𝜇m	Loss of honeycomb pattern. Nuclei become dark and are not clearly distinguished	Dermal papillae	Basal cell layer cells have a cuboidal shape containing large rounded nuclei. Mitotic activity can be easily distinguished
Z5	173.00 𝜇m	Epithelial junction, ill-defined papillae and collagen fibers	Transitional epithelium
Z6	193.69 𝜇m	Collagen fibers	Collagen fibers	Loose connective tissue with a rich vascular supply. The deeper layers contain heavy bundles of collagen fibers