TTF1 and non-small cell lung carcinoma: The 2011 IASLC/ATS/ERS lung adenocarcinoma classification recommends using a single adenocarcinoma marker (TTF-1 or Napsin A) and a single squamous marker for NSCLC classification in small biopsy or cytology specimen in the absence of definitive glandular or squamous morphology to reserve tissue [3].