Although some differences in biomarkers between primary and metastatic non-small-cell lung cancer have been described [10], the patient’s subsequent clinical progression, the distinct histological morphology, and the absence of TTF1 in the pancreatic tumor tissue suggest a diagnosis of primary pancreatic neoplasm, leading to a change in treatment to gemcitabine and nab-paclitaxel. Here, TTF1 is linked to non-small cell lung carcinoma.