The majority of human solid tumours do not metastasize when grown subcutaneously in immunocompromised mice; this includes patient-derived xenograft (PDX) models. However, orthotopic implantation of intact tumour tissue can lead to metastasis that mimics that seen in patients. These patient-derived orthotopic xenograft (PDOX) models have a long history and might better recapitulate human tumours than PDX models.