Histopathological observation of the tumors formed by the CSCs. Benign teratoma formed by miPSCs. (a) transplanted subcutaneously. Normal tissue types derived from three germ layers, including squamous epithelium (keratinized ball), skeletal muscle, cartilage and benign glandular epithelium are observed. Sections from the tumors formed by miPS-LLCcm-PD (b) miPS-LLCcm-CH (c) and miPS-LLCcm-Da (d) cells transplanted subcutaneously. Malignant structures are observed in the glandular cavities (square, bottom right in b) composed of multiple abnormal glands, which are crowded back to back exhibiting high nuclear to cytoplasmic ratio, severe nuclear atypia and multiple pathological mitotic figures (asterisks in b–d). Abnormal glands, inside of glandular cavity has necrosis (arrow in c), and large area necrosis (oval in c). Original magnification was 20X and 40X (a–d). (e) Immunohistochemical analysis showed malignancies with highly proliferative areas strongly stained for Ki-67 and poorly differentiated areas, poorly stained for CK and strongly for Sox2 in the tumor formed by miPS-LLCcm-PD, miPS-LLCcm-CH and miPS-LLCcm-Da when compared with the benign teratoma formed by miPSCs.