Differentiation of ALL from AML

• Auer rods

  • Red toothpick looking things in the cytoplasm

  • They are abnormal azurophilic granules

  • Intensely peroxidase (+)

  • Say for sure that you are looking at myeloid differentiation

• Telling ALL from AML

  • It’s important to tell them apart because they are treated very differently

  • Myeloblasts tend to have more delicate chromatin, prominent or multiple nucleoli, and fine azurophilic granules in the cytoplasm…Auer rods are a sure thing

  • TdT

    • Terminal deoxynucleotidyl transferase, a DNA polymerase

    • Seen in 95% of ALL and <>

  • Myeloid monoclonal antibodies (CD33, CD13, CD11, etc) are reactive in most (80%) of AML; they are rare in ALL and when they are there it’s not good

  • Special stains

    • PAS: “block” positivity in lymphoblasts, diffuse positivity in erythroblasts

    • MP: myeloblasts

    • SB: myeloblasts

    • NSE: monoblasts

Category: Medical Subject Notes , Pathology Notes