['Cryptogenic stroke is common in patients with cancer. Autopsy studies suggest that many of these cases may be because of marantic endocarditis, which is closely linked to cancer activity. We, therefore, hypothesized that among patients with cancer and ischemic stroke, those with cryptogenic stroke would have shorter survival.', 'We retrospectively analyzed all adult patients with active systemic cancer diagnosed with acute ischemic stroke at a tertiary care cancer center from 2005 through 2009. Two neurologists determined stroke mechanisms by consensus. Patients were diagnosed with cryptogenic stroke if no specific mechanism could be determined. The diagnosis of marantic endocarditis was restricted to patients with cardiac vegetations on echocardiography or autopsy and negative blood cultures. Patients were followed until July 31, 2012, for the primary outcome of death. Kaplan-Meier statistics and the log-rank test were used to compare survival between patients with cryptogenic stroke and patients with known stroke mechanisms. Multivariate Cox proportional hazard analysis evaluated the association between cryptogenic stroke and death after adjusting for potential confounders.', 'Among 263 patients with cancer and ischemic stroke, 133 (51%) were cryptogenic. Median survival in patients with cryptogenic stroke was 55 days (interquartile range, 21-240) versus 147 days (interquartile range, 33-735) in patients with known stroke mechanisms (P<0.01). Cryptogenic stroke was independently associated with death (hazard ratio, 1.64; 95% confidence interval, 1.25-2.14) after adjusting for age, systemic metastases, adenocarcinoma histology, and functional status.'] Does cryptogenic subtype predict reduced survival among cancer patients with ischemic stroke?