PTEN and neoplasm: However, the rapid progression to clinical endpoint due to excess ascites production and spread of cells within the peritoneal fluid, rather than bona fide invasion, renders it poorly suited to determine contributions to metastasis, particularly in the case of Pten‐null tumours due to rapid progression (Trp53−/−;Pten−/−, 34 days; Trp53−/−, 47 days; Parental ID8, ~ 100 days) (Walton et al, 2016, 2017).