Fig. 4

Immunohistochemical features of the resected tumor. Marked immunoreactivity of CK5/6, an epithelial and basaloid marker, was observed in the squamous carcinoma component. Marked immunoreactivity of Ki-67, a biomarker that reflects the proliferative activity of a cell, was observed in approximately 70% of the squamous carcinoma nuclei, which indicates the malignant proliferative growth pattern of the tumor. Marked immunoreactivity of P40 (a tumor suppressor protein) was observed in the carcinomatous component