Histologic differences between in situ and embolized carotid web thrombi: a case report

The significance of carotid webs (CaWs) in ischemic stroke is becoming acknowledged. Histological features of clot composition in situ and secondary cerebrovascular embolized thrombi caused by CaW have not been described concurrently. Understanding clots' histological composition is essential for understanding the pathophysiology of clot formation in CaW.

A 50-year-old male patient with acute ischemic stroke, which was believed to be caused by ipsilateral CaW, was admitted to the hospital. Mechanical thrombectomy was used to retrieve thromboemboli from the middle cerebral artery. One month thereafter, the patient underwent carotid endarterectomy, and in situ CaW thrombi were retrieved. Histological analysis by hematoxylin and eosin staining revealed that histopathologic embolized thrombi appeared as typical mixed thrombi, 46.03% fibrin/platelet ratio, 48.12% RBCs, and 5.85% white blood cells. In situ thrombi had a higher fibrin/platelet ratio (68.0%), fewer RBCs (17.2%), and 14.8% white blood cells.

The histopathology of large vessel occlusion stroke embolized thrombi by CaW is similar to that of other stroke etiologies. However, the clot composition of embolized thrombi significantly differs from that of in situ thrombi. CaW's in situ thrombi showed predominantly fibrin, and embolized thrombi had equivalent contents of red blood cells and fibrin/platelets. Histopathological differences between in situ and embolized thrombi suggest new research directions for the etiology of embolization. Further studies are required to confirm these results.