However, it must be kept in mind the possibility of the presence of relatively rare and highly debated entities such as the primary intracranial neuroendocrine carcinoma arising in sellar region (which is TTF1−)⁠ or the small cell carcinoma of unknown primary (SCUP, which is TTF1+) [22]⁠. The gene discussed is TTF1; the disease is small cell carcinoma.