APML (M3)

Acute Promyelocytic Leukemia

• FAB system defines acute promyelocytic leukemia (APL) solely by morphologic criteria.
  
  
• Leukemic infiltrate is composed of abnormal promyelocytes with heavy granulation, sometimes obscuring the nucleus.
  
  
• Often abundant cytoplasm (color plate 153).
  
  
• Auer rods are frequently seen.
  
  
• May have bundles or stacks of Auer rods called faggot cells.
  
  
• Nucleus varies in size and shape and is often reniform (kidney shaped ) or bilobed.
  
  
• React strongly positive with peroxidase stain or Sudan black.
  
  
• Usually are NSE negative.
  
  
• High incidence of DIC due to abnormal promyeloctes rich in thromboplastic substances.
  
  
• Prolonged PT/PTT, increase in fibrinogen degradation products, decreased serum fibrinogen and factor 5.
  
  
• Thrombocytopenia almost always seen.
  
  
• Schistocytes sometimes seen.
  
  
• Translocation of (t[15:17]) unique to APL only.
  
  
• Due to complication associated with DIC, it is important to distinguish APL from other AMLs. Put on anticoagulation therapy.
  
  

PROGNOSIS

Start on heparin therapy immediately; poor future - high mortality due to hemorrhage (intracranial)