Periodic acid schiff stain shows block positivity with following cell line:

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), Lichtman's Atlas of Hematology.