NEC: neuroendocrine carcinoma; PDC: poorly differentiated carcinoma; SCC: squamous cell carcinoma; MM: malignant melanoma; GFAP: glial fibrillary acidic protein; PanCK: pan-cytokeratin; CK7: cytokeratin 7; CK20: cytokeratin 20; TTF-1: thyroid transcription factor 1; Syn: synaptophysin; Chr: chromogranin; LCA: leukocyte common antigen; CD56: cluster of differentiation 56; CDX2: caudal type homeobox transcription factor 2; Melan-A: melanoma antigen; ER: estrogen receptor. The gene discussed is KRT20; the disease is neuroendocrine carcinoma.