Figure 2. Features of a nodular basal cell carcinoma (BCC) as compared to the normal adnexal structures: A) FFOCT image shows a big BCC nodule (yellow asterisk) surrounded by normal skin structures. B) Zoomed-in area from the red box in the image (A) shows cellular features of BCC with nuclear atypia, peripheral palisading (green arrow), and clefting (yellow arrow). The nodule is surrounded by a thick bright band of collagen (red arrows). Sebaceous glands (orange asterisks) have a lobulated appearance with bright punctate structures. The hair follicles (pink arrows) appear round to oval with a central lumen and epidermal lining. C) Corresponding H&E-stained histopathology image. Scale bars = 1 mm.
In sBCC the tumor nodules were seen attached to the epidermis (Figure 3a) . In nBCC (Figure 2) and mnBCC (Figure 3b) , the nodules were identified within the bright dermis. Palisading and clefting were prominent in both nBCC and mnBCCs. Necrosis was seen in the bigger tumor nodules of nBCC as dissociated cells with some scattered bright particles within. The collagen appeared as bright (hyper-reflective) parallel bundles around the tumor nodules. iBCC had a distinct appearance (Figure 3c) . The tumor foci appear as darkish irregular strands (varied size and shape) composed of grayish clusters of cells with intervening bright strands of fibrous tissue. It was easier to identify these strands when they were clustered. Isolated foci were not readily detected. Additionally, in the area of iBCC, there was a complete loss of normal skin structures.