Blasts – myeloid

Myeloblast Granulated blast Abnormal Blasts, POX-positive

Size µm Size µm Size µm Blasts with brown dye pre­ 12–16 12–16 16–20 cipitates of varied density. Nucleus shape Nucleus shape Nucleus shape Remark: All from round/oval round/oval oval the promyelocyte stage on Cytoplasm Cytoplasm Cytoplasm are POX +. basophilic, no granulation, reddish granules, Golgi zone Ø, dense, coarse, purple-red (POX +, esterase Ø) (POX +, esterase Ø) granulation, (POX ++, esterase Ø) Incidence* Incidence* physiologic, AML, MDS, CML AML, RAEB Incidence* AML-M3

Blast with Auer rods Blast with Auer rods and Auer bodies Faggot cell (M3) Lobulated Blast (M3V)

Size µm Size µm Size µm Size µm 14–16 14–16 14–18 16–20 Nucleus shape Nucleus shape Nucleus shape Nucleus shape round/oval round/oval round/oval/lobulated (bi-)lobulated Cytoplasm Cytoplasm Cytoplasm Cytoplasm needle-shaped red inclusions spherical red inclusions (Auer bundles of Auer rods, often fine reddish granulation, (Auer rods), (POX +, esterase Ø) bodies), additionally Auer rods, (POX +, esterase Ø) bundles of Auer rods +/–, (POX +, esterase Ø) (POX +, esterase Ø) Incidence* Incidence* AML-M1, -M2, -M3, -M6, Incidence* AML-M3 and -M3V, t(15;17) Incidence* RAEB-2 AML-M1, -M2, -M6 AML-M3V, t(15;17)

Monoblast (1), (2) Promonocyte Blast, esterase positive

Size µm Monoblast Size µm Blast with precipitates of brown 14–18 description: see to the left 14–18 dye; diagnostic for monoblastic AML only in case of diffuse and Nucleus shape Promonocyte Nucleus shape strong staining. round/oval, 2 description: see to the right lobed, intermediate chromatin nucleoli +/– Cytoplasm Cytoplasm abundant cytoplasm, granula- abundant cytoplasm, fine tion +/–, often vacuoles, granules +/–, pseudopodia +/–, haemophagocytosis +/–, (POX Ø, esterase +) (POX Ø, esterase +) Incidence* Incidence* AML-M5A and -B, -M4, CMML 1 AML-M5A and -B, -M4, CMML

Monocytoid blast (M4) Monocytoid blast (M5B) Abnormal (M4 Eo) Cup-like blast

Size µm Size µm Size µm Size µm 16–18 16–18 14–16 14–16 Nucleus shape Nucleus shape Nucleus shape Nucleus shape monocytoid monocytoid round/oval Nucleus with invaginated intermediate chromatin ­cytoplasm** Cytoplasm Cytoplasm abundant cytoplasm, granula- abundant cytoplasm, granula- Cytoplasm Cytoplasm tion +/–, often vacuoles, tion +/–, often vacuoles, coarse, round, eosinophilic Granulated cytoplasm. Crucial (POX Ø, esterase +) (POX Ø, esterase +) and blue-purple granules, is the nucleus: fingerprint-like (chloroacetate esterase +) indentation; POX + Incidence* Incidence* Incidence* AML-M5A and -B, -M4, CMML AML-M5A and -B, -M4, CMML Incidence* AML with NPM1- and FLT3- AML-M4 Eo, inv(16), t(16;16) mutations

Abnormal (M6) Abnormal (M7) Basophilic blast blast

Size µm Size µm Size µm Size µm 14–16 12–18 14 –16 14–16 Nucleus shape Nucleus shape Nucleus shape Nucleus shape round/oval round/oval often blurred often blurred Cytoplasm Cytoplasm Cytoplasm Cytoplasm deep basophilic, flaky Golgi undifferentiated blast, no blue-purple granulation, often basophilic granules +/–, zone, (POX Ø, esterase Ø) granulation, cytoplasmic vacuoles, (toluidine blue +) (toluidine blue +) blebbing or pseudopodia, Incidence* Incidence* Incidence* (POX Ø, esterase Ø) AML-M6 acute basophilic leukaemia mast cell leukaemia Incidence* AML-M7

* For pragmatic reasons, the abbreviations of FAB classification diagnoses have been used. The WHO classification equivalents are as follows:M0 – AML with minimal differentiation; M1 – AML without maturation; M2 – AML with maturation; M3 – acute promyelocytic leukaemia; M4 – acute myelomonocytic leukaemia; M5 – acute monoblastic and monocytic leukaemia; M6 – acute erythroid leukaemia/proerythroblastic leukaemia; M7 – acute megakaryoblastic leukaemia. ** Invagination of the POX + cytoplasm into the nucleus. Definition of the cup-like blast population: indentation zone≥ 25% of the nuclear surface, ≥10% of blasts show goblet-shaped, usually light indentations. If cup-like blasts are identified, mutation analysis of NMP1 and FLT3 should be performed.

Common cytologic features Nucleus Cytoplasm Quantification of blasts ■ Shape: round/oval ■ Basophilic ■ <1% in PB and <5% in BM: ■ Nuclear-cytoplasmic ratio: 70–90% ■ Reddish granulation +/– in MDS: RA, RCMD +/– ring sideroblasts ■ Chromatin: predominantly regularly distributed, ■ Auer rods +/–; when +, evident for: ■ <5% in PB and 5–9% in BM: RAEB-1 not clumped, not condensed AML, if blasts ≥20% ■ 5–19% in PB and 10–19% in BM: RAEB-2 ■ Varying numbers of nucleoli; may be hidden RAEB-2, if blasts <20% ■ ≥20% in PB and/or BM: acute leukaemia by chromatin

© Copyright 2014 – Universitätsklinikum Aachen AÖR, Klinik für Onkologie, Hämatologie und Stammzelltransplantation Authors: Prof. Dr. med. Roland Fuchs, Reinhild Herwartz, Klinik für Onkologie, Hämatologie und Stammzelltransplantation, Universitätsklinikum Aachen

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