<prompt> Which of the following subtype of AML is characterized by gum hyperplasia, bleeding and visceral infiltration?MonocyticPromyelocyticMegakaryocyticErythrocytic  <response>: Ans. a Monocytic AML. Ref. Robbins, Pathology, 8th ed. Table 12-11A ; 7th ed.,692Revised FAB Classification of Acute Myelogenous Leukemias AMLCLASSDEFINITIONINCIDENCE MORPHOLOGYCOMMENTSM0Minimally differentiated AML2-3Blasts lack Auer rods and myeloperoxidase but express myeloid lineage surface markers.M1AML without maturation20Some blasts 3 are myeloperoxidase positive; few granules or Auer rods and very little maturation beyond the myelo- blast stage of differentiation.M2AML with maturation30-4020 of marrow cells are myeloblasts, but many cells are seen at later stages of granulocyte differentiation;Auer rods are usually present; often associated with t8;21.M3Acute pro- myelocytic leukemia5-10Most cells are abnormal promyelocytes, often containing many Auer rods per cell; patients are younger on average median age 35-40yr; high incidence of DIC; strongly associated with t15;17.M4Acute myelomono- cytic leukemia15-20Myelocytic and monocytic differentiation evident by cytochemical stains; monoblasts are positive for nonspecific esterase; myeloid cells show a range of maturation; variable numbers of Auer rods; subset associated with inv16.M5Acute monocytic leukemia10Monoblasts and immature monocytic cells myeloperoxidase negative, nonspecific esterase positive predominate;Auer rods are usually absent;older patients;more likely to be associated with organomegaly,adenopathy, and tissue infiltration; the M5b subtype is defined by the predominance of mature-appearing monocytes in the peripheral blood, whereas only immature cells are seen in the M5a subtype.M6Acute erythro leukemia5Most commonly associated with abundant dysplastic erythroid progenitors; 20 of cells of the marrow nonerythroid cells are myeloblasts, which may contain Auer rods; usually occurs in advanced age or following exposure to mutagens e.g., chemotherapy.M7Acute megakaryo- cytic leukemia1Blasts of megakaryocytic lineage predominate, as judged by expression of platelet-specific antigens;myelofibrosis or increased marrow reticulin often present;Auer rods are absent. 