In addition, some tissue specific markers, such as TTF-1 and Napsin A for lung adenocarcinoma, CDX-2 and SATB2 for colorectal cancer, PAX-8 and TTF-1 for thyroid cancer, are often negative in thymic adenocarcinoma.[8] But, in this case, we for the second time reported that TTF-1 was positive in some tumor cells, which confirmed previous report in primary thymic papillary adenocarcinoma.[5] Therefore, a thymic adenocarcinoma with TTF-1 positive may not necessarily be a metastasis of lung or thyroid adenocarcinoma. Here, TTF1 is linked to papillary thymic adenocarcinoma.