Blood flow was impeded by a mass adopting the structure of a thick transverse cable. (A) Light microscopy showed the formation of a large transverse occlusive mass that spanned the entire cross-section (640 μm). Blood flow direction is indicated by the “flow” arrow. This mass was the most flow-resisting part of the thrombus. (B) Light microscopy of air-exposed thrombus showed islets attached to the glass slide downstream to the cable, previously obscured by blood. ∗A crosscurrent mass downstream to the islets, likely obscured by blood, could only be observed after glass slide removal. (C) Low-magnification SEM of thrombi revealed that the occlusive mass adopted the structure of a thick transverse cable unseen with light microscopy.