Interestingly, the immunohistochemistry analysis for the stem cell marker POU5F1/OCT4 and the thyroid differentiation marker TG on consecutive paraffin-embedded tumor spheroids sections allowed us to demonstrate that POU5F1/OCT4 cells mostly located in the centre while TG cells at the periphery of the spheroids (Figure 4, Panel B). The gene discussed is POU5F1; the disease is neoplasm.