FAB Classification

M0 Myeloid

undifferentiated blasts, AML — not otherwise categorized

M1 myeloid

blasts and promyelocytes predominate wo further maturation of myeloid cells

M2 myeloid

myeloid cells demonstrate maturation beyond the blast and promyelocyte stage

M3 promyelocytic

promyelocytes predominate in the bone marrow

M4 myelomonocytic

both myeloid and monocytic cells are present to the extent of at least 20% of total leukocytes

M5 monocytic

• most cells are monocytic

• 2 subtypes are recognized, one: large blasts in bone marrow and PB, the other: (differentiated type) by monoblasts, promonocytes, monocytes

M6 erythroleukemia

• aka Di Guglielmo syndrome

• abnormal proliferation of both erythroid and granulocytic precursors

• may include abnormal megakaryocytic and monocytic proliferations

M7 megakaryocytic

large and small megalaryoblasts with a high nuclear-cytoplasmic ratio; pale, agranular cytoplasm

L1 homogenous

• one population of cells w/in the case

• small cells predominant

• nuclear shape: regular with occasional cleft

• chromatin pattern: homogenous

• nucleoli: rarely visible

• cytoplasm: moderately basophilic

L2 heterogenous

• large cells w/ an irregular nuclear shape

• clefts in the nucleus common

• one or more large nucleoli

• cytoplasm varies in color

L3 Burkitt lymphoma type

• cells are large & homogeneous in size

• nuclear shape: round or oval

• nucleoli: 1-3 prominent

• cytoplasm: deeply basophilic with vacuoles often prominent

L1 acute lymphoblastic

principally pediatric