H&E images are shown for the RC-MSK-008, RC-MSK-002, RC-MSK-023, and RC-MSK-001 tumoroid lines. Left panels display the primary patient tumor from which the tumoroid was derived once per patient. Middle panels display the tumoroids in 3D culture. Right panels display the engrafted tumoroids within the mouse rectum following endoluminal transplantation The number of mice engrafted with indicated tumoroids is 8, 7, 8, and 5 (top to bottom). The H&E photomicrographs demonstrate histopathologic conservation of glandular features as noted in the human adenocarcinomas from which they were derived. Scale bar, 50 μm.