The purpose of this study is to better understand the causes of stroke in people with cancer. Active cancer increases the risk of stroke. The investigators do not know exactly why this occurs but one possible reason is that people with cancer may have thicker blood than people without cancer. Thick blood can sometimes cause blood clots to form in the heart, which can then travel to the brain and cause stroke. This study is being done to help figure out why this and other causes of stroke occur in people with cancer. The investigators expect that information from this study will help doctors to more effectively prevent and treat stroke in individuals with cancer.

This will be a prospective cross-sectional study to examine the unique mechanisms of ischemic stroke in cancer patients. Enrollment will occur at the NewYork-Presbyterian Hospital (NYPH)/Weill Cornell Medical Center (WCMC) and the Memorial Sloan Kettering Cancer Center (MSKCC). Measurements will occur at the NYPH/WCMC and MSKCC Neurovascular Ultrasound Laboratories, the MSKCC Central Laboratory, and the Sharp Laboratory at the University of California, Davis. Three groups of adult patients will be enrolled. Group 1 will consist of consecutive patients with active solid tumor cancer and acute ischemic stroke. Group 2 will be patients with acute ischemic stroke and no cancer. Patients in Groups 1 and 2 will be enrolled at 96 hours +/- 24 hours of stroke onset. Group 3 will include patients with active solid tumor cancer and no stroke. This group will allow us to confirm that differences between stroke patients with and without cancer are not simply incidental findings that can be expected in all cancer patients regardless of thrombotic status. Demographics, comorbidities, and stroke severity (for Groups 1 and 2 only) will be recorded on admission using a structured form. Study patients will undergo three facets of testing: 1) Transcranial Doppler (TCD) microemboli detection; 2) hematological biomarker testing; 3) peripheral blood leukocyte RNA gene expression analysis.

Inclusion Criteria

• 18 years of age or older
• Active solid tumor cancer (for Groups 1 and 3 only)
• MRI confirmed acute ischemic stroke (for Groups 1 and 2 only)
• Available for blood draw at 96 hours (+/- 24 hours) from last known well time (for Groups 1 and 2 only) or within 2 weeks of enrollment (for Group 3)
• Available for TCD within 2 weeks of enrollment

Exclusion Criteria

• Primary brain tumor or hematological cancer
• Treatment with intravenous or intraarterial thrombolysis or mechanical embolectomy
• Platelets < 50,000/mm3
• Hemodialysis within 14 days
• Active pregnancy
• Infection within 14 days per Infectious Diseases Society of America (IDSA) criteria

We plan to enroll three groups of 50 patients each. Group 1 will consist of patients with acute ischemic stroke and active solid tumor cancer, Group 2 will include patients with acute ischemic stroke and no cancer, and Group 3 will include patients with active solid tumor cancer and no stroke.