Fig. 2.

PaCSs are widespread in cells of Philadelphia-negative MPN. a PaCSs in PB platelets of a patient with PV, enlarged in the inset to show barrel-like particles and FK1 immunoreactivity. b BM megakaryocyte with small FK1-reactive peripheral PaCSs, enlarged in the inset, from a patient with ET. c A fibroblast (f) with FK1-positive PaCSs and two intrasinusoidal erythroblasts (asterisks) are found in the BM of an individual with PMF. The fibroblast is enlarged in c1 and c2 to show the intracellular procollagen granules (arrows), juxtafibroblast collagen fibers (arrowheads), and FK1-positive PaCSs