Fig 2: The expression patterns of biomarkers in oral verrucous carcinoma (OVC) and squamous cell carcinoma (OSCC). a A representative specimen of oral verrucous carcinoma (OVC) (HE). This tumor shows near-total loss of CK13 (CK13 pattern C), with intense CK17 in all tumor cells (CK17 pattern C). The expression pattern of Ki-67 in the adjacent non-tumor epithelium (Epi) is predominantly suprabasal (Ki-67 pattern A, arrows). In tumor tissues (T), the Ki-67-labeled cells are mainly detected in both basal and parabasal layers (Ki-67 pattern C, arrowheads). Cytoplasmic Ln5?2 expression is expressed in tumor cells at the invasion front (Ln5?2 pattern C, arrows), with an irregular, discontinuous basement membrane-like structure noted (arrowheads). b A representative specimen of oral squamous cell carcinoma (OSCC) (HE), with very weak expression of CK13 in tumor nests (T) (CK13 pattern C). Strong immune-reactivity of CK17 is also noted in the tumor nests (CK17 pattern C). Ki-67-labeled tumor cells are mainly detected in the basal layer (Ki-67 pattern B, arrows), with strong cytoplasmic staining of Ln5?2 in almost all of the outer/peripheral tumor cells in the tumor nests (Ln5?2 pattern D, arrowheads). HE, hematoxylin–eosin stain. Epi, non-tumor epithelia. T, tumor

Fig 3: The expression patterns of biomarkers in non-tumor epithelia. a The histological picture of a nearly normal buccal mucosa (HE), showing a homogenous CK13 expression from the suprabasal layer (CK13 pattern A), absent CK17 expression (CK17 pattern B). The ki-67-labeled epithelial cells are confined to the suprabasal layers (Ki-67 pattern A). Ln5?2 is barely detected at the junction between the epithelium and underlying connective tissue (Ln5?2 pattern A1, arrow). b In an acanthotic epithelium (HE stain), decreased expression of CK13 is noted (CK13 pattern B), while expression of CK17 is increased (CK17 pattern B). The ki-67 positivity remains predominantly in the suprabasal layers (Ki-67 pattern A, magnified in the lower middle figure). A clear, uninterrupted staining of Ln5?2 in the basement membrane is noted (Ln5?2 pattern A2, arrows). HE, hematoxylin–eosin stain