Cryopreservation preserves tumor tissue by cooling the sample to very low temperatures. While it is scientifically possible to revive (or warm) cryopreserved tissue and develop patient-derived xenograft orthotopic models from it, the success of that approach depends greatly on the method of cryopreservation, the size of the tumor tissue sample (a minimum of one cubic centimeter) and its condition. At Certis, we prefer to work with fresh tumor tissue (received and engrafted within 24 hours of biopsy or resection surgery) to maximize the likelihood of success.