Acute myeloblastic leukemia (M0,M1, M2) | Myeloblasts range from 20 to 90% of marrow cells. Cytoplasm occasionally contains Auer bodies. Nucleus shows fine reticular pattern and distinct nucleolus (1 or 2 usually). Blast cells are sudanophilic. They are positive for myeloperoxidase and chloroacetate esterase, negative for nonspecific esterase, and negative or diffusely positive for PAS (no clumps or blocks). Electron microscopy shows cytoplasmic primary granules. | Most common in adults, and most frequent variety in infants. Three morphologic-cytochemical types (M0, M1, M2) | Chromosomes +8, –5, –7, del(11q) and complex abnormalities common. RUNX1(AML1) and FLT3 mutations occur in approximately 20 to 25% of cases. M0 type blast cells positive with antibody to myeloperoxidase and anti-CD34 and CD13 or CD33 coexpression. AML1 mutations in ~25%. M1 expresses CD13 and CD33. Positive for myeloperoxidase by cytochemistry. M2 AML with maturation often associated with t(8;21) karyotype. M2 AML with t(6;9)(p23;q34), an uncommon variant, is associated with marrow basophilia, a high blast count, a high frequency of FLT3-ITD, and a poor outcome. |
Acute promyelocytic leukemia (M3, M3v) | Leukemic cells resemble promyelocytes. They have large atypical primary granules and a kidney-shaped nucleus. Branched or adherent Auer rods are common. Peroxidase stain intensely positive. A variant has microgranules (M3v), otherwise the same course and prognosis. | Usually in adults. Hypofibrinogenemia and hemorrhage common. Leukemic cells mature in response to all-trans-retinoic acid. | Cell contains t(15;17) or other translocation involving chromosome 17 (RAR-α gene). Cells are HLA-DR negative. |
Acute myelomonocytic leukemia (M4, M4Eo) | Both myeloblastic and monoblastic leukemic cells in blood and marrow. Peroxidase-, Sudan-, chloroacetate esterase-, and nonspecific esterase-positive cells. M4Eo variant has marrow eosinophilia. | Similar to myeloblastic leukemia but with more frequent extramedullary disease. Mildly elevated serum and urine lysozyme. | Leukemic cells in eosinophilic variant (M4Eo) usually have inversion or translocation of chromosome 16. |
Acute monocytic leukemia (M5) | Leukemia cells are large; nuclear cytoplasmic ratio lower than myeloblast. Cytoplasm contains fine granules. Auer rods are rare. Nucleus is convoluted and cell simulates promonocytes (M5a) or may simulate monoblasts (M5b) and contain large nucleoli. Nonspecific esterase-positive inhibited by NaF; Sudan-, peroxidase-, and chloroacetate esterase-negative. PAS occurs in granules, blocks. | Seen in children or young adults. Gum, CNS, lymph node, and extramedullary infiltrations are common. DIC occurs. Plasma and urine lysozyme elevated. Hyperleukocytosis common. | t(4;11) common in infants. Rearrangement of q11;q23 very frequent. |
Acute erythroid leukemia (M6) | Abnormal erythroblasts are in abundance initially in marrow and often in blood. Later the morphologic findings may be indistinguishable from those of AML. | Pancytopenia common at diagnosis. | Cells reactive with antihemoglobin antibody. Erythroblasts usually are strongly PAS and CD71-positive, express ABH blood group antigens. Cells reactive with anti–Rc-84 (antihuman erythroleukemia cell-line antigen). |
Acute megakaryocytic leukemia (M7) | Small blasts with pale agranular cytoplasm and cytoplasmic blebs. May mimic lymphoblasts of medium to larger size. Leukemic cells with megakaryocytic morphology may coexist with megakaryoblasts. | Usually presents with pancytopenia. Markedly elevated serum lactic acid dehydrogenase levels. Marrow aspirates are usually "dry taps" because of the invariable presence of myelofibrosis. Common phenotype in the AML of Down syndrome. | Antigens of von Willebrand factor, and glycoprotein Ib (CD42), IIb/IIIa (CD41), IIIa (CD61) on blast cells. Platelet peroxidase positive. |
Acute eosinophilic leukemia | Mixture of blasts and cells with dysmorphic eosinophilic granules (smaller and less refractile). | Hepatomegaly, splenomegaly, lymphadenopathy may be prominent. Absence of neurologic, respiratory, or cardiac signs or symptoms characteristic of chronic eosinophilic leukemia (clonal hypereosinophilic syndrome). | Cyanide-resistant peroxidase stains eosinophilic granules. TEM shows eosinophilic granules to be smaller and missing central crystalloid. Biopsy may show Charcot-Leyden crystals in skin, marrow, or other sites of eosinophil accumulation. |
Acute basophilic leukemia | Mixture of blast cells and cells with basophilic granules in blood and marrow. | Often has hepatomegaly and or splenomegaly; symptoms often present. Rash with urticaria, headaches, prominent gastrointestinal symptoms. | CD9 + CD25 + CD33 + CD123+ cells are usually present. Toluidine blue-positive cells. Hyperhistaminemia and hyperhistaminuria. Cells negative for tryptase but positive for histidine decarboxylase. |
Acute mast cell leukemia | Mast cells in blood and marrow. Most contain granules but some are agranular and may simulate monocytes. | Fever, headache, flushing of face and trunk, pruritus may be present. Abdominal pain, peptic ulcer, bone pain, diarrhea more common than other AML subtypes. Hepatomegaly, splenomegaly common. Hemorrhagic diathesis may be evident. | CD13, CD33, CD68, CD117 often positive. Cells positive for tryptase staining and serum tryptase elevated. Hyperhistaminemia and hyperhistaminuria. |