Undifferentiated acute leukemia, peripheral blood. Three blasts are seen in the center of the field and a somewhat abnormal neutrophil is seen peripherally.


Acute nonlymphoblastic leukemia, FAB classification M0, bone marrow aspirate from a 69-year-old man. The blasts are small or medium sized with no visible cytoplasmic granules, and few are nucleolated. The myeloperoxidase and nonspecific esterase reactions were negative. The myeloid nature of the blasts was documented by (1) immunophenotype expression of CD13, CD33, positive reaction with a monoclonal antibody against myeloperoxidase (anti-MPO), and negative lymphoid markers; and (2) ultrastructural cytochemistry, which demonstrated peroxidase activity localized in small granules.


Acute nonlymphoblastic leukemia, FAB classification M1, bone marrow aspirate. Virtually all of the cells in the bone marrow were myeloblasts. There was little evidence of maturation beyond the myeloblast stage. Several myeloblasts contain azurophilic granules, and occasional Auer rods are identified.


Acute nonlymphoblastic leukemia, FAB classification M2, bone marrow aspirate. The blast cells in this marrow contain abundant azurophilic granulation. Numerous long, slender Auer rods are also illustrated in this field. These findings are suggestive of the t(8;21) chromosome abnormality.


Translocation (8;21). This karyotype is from the patient with M2 acute nonlymphoblastic leukemia whose bone marrow is seen in slide 64.


Hypogranular acute promyelocytic leukemia, FAB classification M3, bone marrow aspirate. The myeloblast in the central portion of the photograph contains numerous Auer rods. This cell is referred to as a faggot cell and is found in approximately 90 95% of patients with acute promyelocytic leukemia.


Translocation (15;17) characteristic of M3 acute leukemia.

Acute nonlymphoblastic leukemia, FAB classification M4, bone marrow aspirate. The large abnormal blast on  the left has distinct monocytoid features, some membrane irregularity, and some cytoplasmic vacuoles as well as gray cytoplasm. The two blasts on the right have very immature nuclear chromatin, nucleoli, and some cellular granules. They are clearly myeloid rather than monocytoid. Thus this field illustrates the two lineages that are characteristic of M4 acute leukemia.


Acute nonlymphoblastic leukemia, FAB classification M4Eo, bone marrow. It is associated with an inversion of the long arm of chromosome 16. In addition to the promonocytes and blast forms, there are many abnormal eosinophils, some of which have coarse basophilic granules.


Acute nonlymphoblastic leukemia, FAB classification M5a (L) and M5b (R). The M5a blasts have a moderate amount of cytoplasm and somewhat coarse nuclei. The nucleoli are not unusually prominent. The blasts were positive with the nonspecific esterase stain, and the patient had an associated t(9;11) chromosome abnormality. The predominant M5b cell is a promonocyte. This cell is characterized by abundant cytoplasm with numerous scattered azurophilic granules and a nucleus with finely dispersed nuclear chromatin. The nuclei are marked by extensive lobulation and creasing. Some of the nuclei have a cerebriform appearance.



Acute nonlymphoblastic leukemia (ANLL), FAB classification M5 with erythrophagocytosis, bone marrow aspirate. This morphological entity is associated with a specific reciprocal translocation that involves the short arms of chromosome t(8;16)(p11;p13).


Acute nonlymphoblastic leukemia, FAB classification M6, bone marrow aspirate. The giant multinucleated abnormal erythroblast is the striking feature of this field. Next to it one can also appreciate a somewhat distorted myeloblast.


Acute nonlymphoblastic leukemia, FAB classification M7, peripheral blood. The pleomorphism of the leukemic megakaryoblasts, clearly apparent in this photomicrograph, demonstrates why precise diagnosis of this type of acute leukemia is difficult.


Therapy-related acute nonlymphoblastic leukemia, FAB classification M1, in a treated myeloma patient, bone marrow aspirate. One myeloma cell and four leukemic myeloblasts are seen in this field.


Biphenotypic (mixed lineage) acute leukemia, bone marrow aspirate, adult. There is a mixture of blasts, some displaying lymphoid features while others are larger, undifferentiated with features suggestive of acute myeloid leukemia. Immunological markers demonstrated that the majority of blasts from this adult patient coexpressed B-lymphoid (CD79a, cytoplasmic CD22, CD10) and myeloid (CD13, CD33, anti-myeloperoxidase [MPO])  antigens and were positive with early hematopoietic associated markers (CD34, HLA-DR and TdT). Morphology of biphenotypic acute leukemia (BAL) is variable with some cases resembling acute lymphoblastic leukemia and others resembling one of the subtypes of acute myeloid leukemia. It is not unusual to find two morphologically distinct blast populations (E. Matutes Haematologica 82:4, 1997). Immunophenotyping is a key diagnostic test for BAL since its recognition has important prognostic implications.