Certis implants both tumor chunk and single-cell suspensions, depending on the circumstances. Certis implants tumor chunks of approximately 2-3mm when possible, as this technique helps preserve the original tumor’s histological architecture and stroma construction, cell-cell ,adhesions, and cell-type composition. Orthotopic engraftment further improves clinical relevance through recapitulation of the tumor microenvironment. If implantation of a tumor chunk is not possible, we use single-cell suspensions. Clinically annotated patient-derived xenograft (PDX) models are generated from tumor cells isolated from the ascites or pleural fluid of patients undergoing clinical procedures. Currently, single-cell suspensions are used for brain, bone and lung model development.