Prior studies have reported TTF1 sensitivity for adenocarcinoma in a range of 75 to 86%.12, 13, 14, 15, 16, 17, 18In the well-differentiated adenocarcinomas, four cases which were negative for TTF1 revealed morphological features of mucinous adenocarcinomas. Here, TTF1 is linked to mucinous adenocarcinoma.