Figure 1. Images of normal layers of the skin. (A) FF-OCT image showing grayish epidermal lining (pink arrow), dermis (green asterisk), and underlying subcutis (pink asterisk). (B) A stratified layer of the epidermis (pink arrow) shows multiple round to oval dark nuclei surrounded by bright (grayish) cytoplasm. The underlying dermis appears grayish (green asterisk). (C) Adipocytes of the subcutis appear as dark polygonal structures separated by thin white septa (pink asterisk). (D-F) Corresponding histopathology section stained with Toluidine blue. Magnifications: (A) = 5.2 mm x 5.2 mm; (B, C) = 300 x 150 mm; (D)= 10x; (E, F) = 40x .
Hair follicles (Supplemental Figure 2) appeared as tubular to round structures with a central dark hole lined by an inner grayish epidermal layer and an outer bright fibrous layer. Sometimes a bright hair shaft was identified in the center of these follicles making their identification easy. Sebaceous glands (Supplemental Figure 2)appeared as round to oval varied-sized darkish (hypo-reflective) structures composed of multiple lobules separated by thin bright (hyper-reflective) fibrous septa. Due to their round shape, these glands were difficult to distinguish from nBCC; however, the presence of multiple small bright punctate particles, which we speculate to be the sebum particulates, aided in the distinction. Eccrine glands (Supplemental Figure 2) appeared as tightly packed clusters of small, round to oval grayish (hypo-reflective) structures separated by thin bright septa. Within the gland’s lumen, small punctate bright particles (similar to sebaceous glands) could be seen. Eccrine ducts (Supplemental Figure 2) were seen within the clusters of eccrine glands as small roundish structures with a central dark (areflective lumen) and lined by grayish cells. The eccrine unit (glands and ducts) could be identified as embedded within dark (areflective) adipose tissue.
Smooth muscles (Supplemental Figure 3) could be identified as bundles of grayish (hypo-reflective) structures with intervening bright thin fibrous bands. Cigar-shaped dark elongated nuclei were seen within the muscle fibers. The smooth muscle bundles were seen lining the dark lumen of medium-sized blood vessels and attached to a hair follicle (as arrector pili muscle).
2) Basal cell carcinoma: Classic features of BCC could be identified on FF-OCT. BCC tumor nodules appeared as round to oval varied size structures composed of clusters of grayish (hyporeflective) pleomorphic cells with dark nuclei (Figures 2, 3) . These tumor nuclei were seen arranged perpendicular at the periphery of the nodule forming “palisading”. Clefting was identified as a dark (areflective area) around tumor nodules.