Histological appearances of intramucosal parts of undifferentiated-type gastric carcinomas (UGCs). A signet ring cell carcinoma (SIG) component with a layered structure in case A107 (a). Small carcinoma cells are distributed in the deeper part just above or in the muscularis mucosae in a SIG component in case M109 (b). A mucinous adenocarcinoma component in case A107 (c). A poorly differentiated adenocarcinoma component in case SM106 (d). Minor tubular components in cases SM105 and SM201, respectively (e, f).