Analysis in immunohistochemistry context revealed a metastatic adenocarcinomatous proliferation with an immunoprofile compatible with a poorly differentiated G3 mucinous adenocarcinoma, most likely of pulmonary origin, with positive thyroid transcription factor 1 (TTF1), intensely positive LIMA’s typically expressed cytokeratin 7 (CK7) (88–94.7%), cytokeratin 20 (CK20) positive at low intensity (79%), negative leukocyte common antigen (LCA) negative, negative caudal type homeobox 2 (CDX2), and negative squamous cell carcinoma specific marker (P40) (Figure 2) [7,8,10]. This evidence concerns the gene KRT20 and mucinous adenocarcinoma.