Hyungjong Park, MD^1,3, Jayoung Kim, MS¹, Jimin Ha, MS¹, In Gun Hwang, MD¹, Tae-Jin Song, MD, PhD², Joonsang Yoo, MD³, Sung Hwan Ahn, MD, PhD⁴, Kyoungsub Kim, MD¹, Byung Moon Kim, MD, PhD⁵, Dong Joon Kim, MD, PhD⁵, Young Dae Kim, MD, PhD¹, Hyo Suk Nam, MD, PhD¹, Il Kwon, PhD¹, Hyun-Jung Choi, PhD⁶, Sung-Il Sohn, MD, PhD³, Hye Sun Lee, PhD⁷, Ji Hoe Heo, MD, PhD<sup>1,*

1</sup> Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
² Department of Neurology, Ewha Womans University School of Medicine, Seoul, Korea
³ Department of Neurology, Keimyung University School of Medicine, Daegu, Korea
⁴ Department of Neurology, Chosun University School of Medicine, Gwanju, Korea
⁵ Department of Radiology, Yonsei University College of Medicine, Seoul, Korea
⁶ Severance Integrative Research Institute for Cerebral & Cardiovascular Diseases, Yonsei University College of Medicine, Seoul, Korea
⁷ Biostatistics Collaboration Unit, Yonsei Universeity College of Medicine, Seoul, Korea

^*Corresponding author: Ji Hoe Heo, MD, PhD, Department of Neurology, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemoon-gu 03722 Seoul, Korea 

The histologic features of thrombus in stroke patients with cancer are not well known. Using immunohistochemical staining of thrombi retrieved during mechanical thrombectomy in stroke patients, thrombus compositions were compared between 16 patients with active cancer, 16 patients with inactive cancer, and 16 patients without any history of cancer. The active cancer group showed higher platelet and lower erythrocyte fractions than the inactive cancer or the control group. Four patients with vegetation showed very high platelet and low erythrocyte fractions. Patients with cryptogenic etiology in the active cancer group showed a similar pattern to those with vegetation. These findings may aid the determination of treatment strategies in cancer‐associated stroke.