Further immunohistochemistry showed tumor cells with strong coexpression of CK5/6 and p63, which are indicators of squamous cell carcinoma (Figure 4(a), dual staining), but negative for p16 (Figure 4(b)), CD117 (indicator of gastrointestinal stromal tumor, Figure 4(c)), and CK7 (indicator of adenocarcinoma, Figure 4(d)). The gene discussed is KRT5; the disease is squamous cell carcinoma.