TTF1 and lung adenocarcinoma: Subsequent immunohistochemical staining revealed TTF-1 positivity in the pancreatic specimen (Figures 4A-4C), and subsequent multi-gene testing using the AmoyDx® Lung Cancer Multi-Gene PCR Panel (Amoy Diagnostics Co., Ltd., Xiamen, China) identified an EGFR exon 19 deletion (E746_A750del), confirming the diagnosis of EGFR-mutated lung adenocarcinoma with pancreatic metastasis.