<prompt> Periodic acid schiff stain shows block positivity with following cell line:MyeloblastsLymphoblastsMonoblastsMegakaryoblasts  <response>: Leukemic lymphoblasts react with periodic acid schiff PAS stain gives reddish-purple clumps, sometimes more rectangular in character and referred to as block positivity as opposed to the fine granular staining that can be seen in some myeloblasts and other cells. Ref: Lichtman M.A., Shafer J.A., Felgar R.E., Wang N. 2007. G. Lymphocytic Leukemias. In M.A. Lichtman, J.A. Shafer, R.E. Felgar, N. Wang Eds, Lichtmans Atlas of Hematology. 