Twenty-three cases without clear morphological diagnostic criteria for SQCC (keratinization or intercellular bridges) were excluded: 7 due to TTF1 positivity, suggestive of adenocarcinoma, 12 due to no or only weak p40 expression in a screening approach as well as in whole slide re-evaluation, insufficient for final diagnosis of SQCC (18), and four cases due to an alternative histological diagnosis on re-evaluation. Here, TTF1 is linked to adenocarcinoma.