The current study, demonstrates for the first time that CTCs from patients with newly diagnosed SCLC could be detected using the TTF-1 and CD56 molecules which are expressed in tumor cells of neuroendocrine origin since both TTF-1 and CD56 are expressed in 89–100%21, 24, 27, 35 and in (90–99%)36, of SCLC cases, respectively. Here, TTF1 is linked to small cell lung carcinoma.