TTF1 and lung carcinoma: Notably, the metastatic foci of this patient showed TTF1 (−), P40 (−), and napsin A (−), excluding a lung cancer origin, but demonstrated strong P504S positivity (3+) and partial PSA positivity, confirming a prostate origin, suggesting tumor clonal heterogeneity, which may stem from the downregulation of the androgen receptor signaling pathway (10).