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Leukemia


KEY FACTS

Terminology

  • Extramedullary leukemic tumors

  • Synonyms: Granulocytic sarcoma, chloroma

Imaging

  • Best diagnostic clue: Homogeneous enhancing tumor(s) in patients with known or suspected myeloproliferative disorder

  • Meningeal (dural-based or pial) > intraparenchymal lesions

  • NECT: Hyperdense

  • CECT: Moderate uniform enhancement

  • MR

    • T2/FLAIR iso- to hypointense

    • Restricted diffusion on DWI

Top Differential Diagnoses

  • Metastatic neuroblastoma

  • Meningioma

  • Extraaxial hematoma

  • Extramedullary hematopoiesis

  • Langerhans cell histiocytosis

Pathology

  • CNS leukemia presents in 3 forms

    • Meningeal disease (usually with acute lymphoblastic leukemia)

    • Intravascular aggregates (leukostasis): Can rupture, hemorrhage with markedly ↑ leukocyte counts

    • Tumor masses (chloroma)

  • Multiple other intracranial manifestations, complications of leukemia/treatment

    • Posterior reversible encephalopathy syndrome (PRES)

    • Posttransplant lymphoproliferative disease after bone marrow transplantation

    • Invasive fungal infection

    • Venous thrombosis associated with chemotherapy

    • Late development of cavernous angiomas after radiation therapy

Diagnostic Checklist

  • Hemorrhagic lesions in children with acute myelogenous leukemia can be chloroma or complication of therapy

Coronal graphic shows multiple foci of leukemic infiltrates in the skull base/paranasal sinuses
, hypothalamus/infundibulum
, basal ganglia
, and dura
. Green color observed at pathology results in the name “chloroma.” The accepted term is “granulocytic sarcoma.”

Axial NECT scan in a child with acute myelogenous leukemia (AML) and a palpable scalp mass shows a hyperdense intra-
and extracranial mass
that centers on the calvaria.

Axial T2WI in a child with AML demonstrates a hypointense parietal mass
surrounded by a collar of edema
. AML with parenchymal metastasis (cerebral granulocytic sarcoma) is rare.

NECT scan in a 5-year-old girl with AML shows chloroma infiltrating both trigeminal nerves, enlarging the cisternal
and Meckel cave segments
.

(Courtesy N. Aggarwal, MD.)

TERMINOLOGY

Abbreviations

  • Extramedullary leukemic tumors (EML)

  • Extramedullary myeloblastoma, extramedullary myeloid cell tumors (EmMCT)

Synonyms

  • Granulocytic sarcoma, chloroma

Definitions

  • Solid tumor of myeloblasts/myelocytes/promyelocytes

    • In patients with myeloproliferative disorder

  • Multiple other intracranial manifestations of leukemia/treatment complications

    • Posterior reversible encephalopathy syndrome (PRES)

    • Invasive fungal infection

    • Late development of cavernous angiomas after radiation therapy

    • Post-transplantation lymphoproliferative disease (PTLD) after bone marrow transplantation

    • Venous thrombosis associated with chemotherapy (L-asparaginase)

    • Vasculitis

      • –

        Primary manifestation of leukemia

      • –

        Secondary to treatment (trans retinoic acid)

      • –

        Secondary to infection (e.g., Aspergillus )

IMAGING

General Features

  • Best diagnostic clue

    • Homogeneous enhancing tumor(s) in patients with known or suspected myeloproliferative disorder

    • Most often complication of acute myelogenous leukemia (AML)

  • Location

    • Meningeal (dural-based or pial) > intraparenchymal lesions

CT Findings

  • NECT

    • Iso-/hyperdense to brain

      • –

        May rapidly become hypodense (necrosis, liquefaction)

    • May present with (or mimic) hematoma

    • Look for skull base/paranasal sinus involvement

  • CECT

    • Homogeneous enhancement

      • –

        Hyperdensity or presence of hemorrhage may mask enhancement

    • May have rim enhancement, mimic abscess

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