<prompt> Periodic acid schiff stain shows Block positivity in -MyeloblastsLymphoblastsMonoblastsMegakaryoblasts  <response>: Lymphoblasts Myeloperoxidase: negative Sudan Black: negative Nonspecific esterase: negative PAS: block positivity Myeloblasts Myeloperoxidase: positive sudan black: positive nonspecific esterase: positive in M4 M5 PAS: negative Ref: RAM DAS NAYAK 2nd Ed. Pg no:293 