Fig. 4.

Microscopic view of the nasopharynx in the control, DMSO, and DNP groups, with lesion areas (indicated by blue solid line boxes) and pathological results, and HE staining revealed the general morphology of the primary lesion areas. CK5 staining was used to visualize the epithelial cell cytoplasm, p63 staining was used to identify basal cell nuclei, and Ki67 staining was used to evaluate cell proliferation. In the control group, the surface of the nasopharyngeal roof and posterior wall appeared very smooth. Pathological findings revealed a normal transition from pseudostratified ciliated columnar epithelium to stratified squamous epithelium (PESE) at the epithelial transition zone (A1-A4, B1-B4). The conditions of the DMSO group were similar to those of the control group (C1-C4, D1-D4). In the DNP group, the nasopharyngeal roof and posterior wall surfaces appeared rough, with nodular elevations and accompanying mucosal congestion. HE staining revealed mildly dilated surrounding blood vessels and reactive hyperplasia of pharyngeal tonsil lymphoid follicles. Focal atypical hyperplasia, characterized by epithelial ingrowth with a subbasement membrane growth tendency, is observed, resulting in irregular arrangement and compromised integrity of basal cells. Cell proliferation is highly active within lesion areas