Lines of zahn are found in

ref Robbins 9/e p125 Thrombi can have grossly (and microscopically) apparent laminations called lines of Zahn; these represent pale platelet and fibrin layers alternating with darker red cell-rich layers. Such lines are significant in that they are only found in thrombi that form in flowing blood; their presence can there- fore usually distinguish antemoem thrombosis from the bland nonlaminated clots that form in the postmoem state. Although thrombi formed in the "low-flow" venous system superficially resemble postmoem clots, careful evaluation generally reveals ill-defined laminations.