TTF1 and small cell lung carcinoma: Subsequent immunohistochemistry after lobectomy confirmed small cell lung carcinoma (SCLC, Fig. 2.B-E), insofar as that TTF-1 (thyroid transcription factor-1) evidenced a pulmonary origin (Fig. 2.E) and Synaptophysin-staining demonstrated neuroendocrine differentiation (Fig. 2.C).