Adenocarcinomas showed a strong positivity for CK7 (Figure 6C) and TTF−1 (Figure 6D); the enteric-type variant also showed focal immunoreactivity for CDX2 and CK20; small cell carcinomas were positive for Synaptophysin, Chromogranin A, CK8/18 and TTF-1, with a very high Ki67 proliferative index; squamous cell carcinomas were positive for CK 5/6, p63 and p40; undifferentiated carcinomas (non-small cell carcinoma—unclassifiable) were positive for CK AE1/AE3, focally for TTF-1, and occasionally stained for CK7, CK 5/6 and p63. This evidence concerns the gene KRT5 and small cell carcinoma.