Pulmonary Adenocarcinoma with Enteric Differentiation without TTF-1 Expression Is a Very Rare Subtype with Limited Treatment Options and Poor Prognosis.

Introduction: Pulmonary adenocarcinoma with enteric differentiation (PAED) without thyroid transcription factor-1 (TTF-1) expression is an extremely rare variant of lung cancer. Due to its rarity, few clinicopathological and molecular studies have been performed on PAED, particularly in Caucasian patients. Therefore, it is necessary to obtain clinicopathological data of Caucasian PAED patients without TTF-1 expression, their systemic therapy options, and the efficacy of their systemic treatment.