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Atlas of Bone Marrow pathology
Mojmir Moulis, Josef Feit et al.
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Acute Myeloid Leukemia (AML)
Introduction

Clonal expansion of myeloid blasts in bone marrow, peripheral blood or other organs.

Etiology
  • viral infections
  • ionizing radiation
  • cytotoxic chemotherapy
  • benzene
  • and other
Clinical signs
  • most often elderly patients (median is 60 years)
  • incidence 10/100.00
  • anemia
  • thrombocytopenia
  • leukocytosis with neutropenia (or leukopenia)
  • infections
  • and other
Classification
  • FAB 1982 — purely morphological classification
  • WHO 2008 — takes cytogenetic abnormalities and prognosis into account (besides morphology)

FAB classification:

  • M0 — Minimally differentiated myeloblastic leukemia
  • M1 — Myeloblastic leukemia without maturation
  • M2 — Myeloblastic leukemia with maturation
  • M3 — Promyelocytic leukemia
  • M4 — Myelomonocytic leukemia
  • M5a — Monoblastic leukemia
  • M5b — Monocytic leukemia
  • M6 — Erythroid leukemia
  • M7 — Megakaryoblastic leukemia

WHO classification:

  • AML with recurrent genetic abnormalities (usually balanced translocations, relatively favourable prognosis, high complete remission rate)
  • AML with multilineage dysplasia (worse prognosis)
  • therapy-related AML (cytotoxic chemotherapy or radation therapy, refractory to antileukemic therapy, short median survival time)
  • AML not otherwise categorized (morphologic clasification similar to the FAB system)
  • AL with double differentiation (bilinear, biphenotypic)
Histology

Bone marrow is markedly hypercellular, sometimes hypocellular (especially therapy-related AML), myelopoiesis is usually markedly increased with a differentiation arrest and increased myeloblast (monoblast) levels above 20%. Megakaryocytes and erythropiesis are residual (except M6 and M7), M7 leukemia causes significant fibrosis.

Most common sites of infiltration are the spleen, liver, lymph nodes and other, however significant organomegaly is uncommon. Sometimes tumoriform lesions (myelosarcoma) may be found.

Secondary symptoms: bleeding, infections, anemia.

Pictures

Acute myeloid leukemia, hypoplastic, bone marrow: Hypoplastic acute myeloic leukemia, HE 100x (73112) Hypoplastic acute myeloic leukemia, PAS 100x (73113)

Acute meyloid leukemia, kidney, infiltration into the glomerulus: Kidney in acute myeloic leukemia, HE 100x (72796)