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Typical Choroid Plexus Papilloma


KEY FACTS

Terminology

  • Choroid plexus tumor (CPT)

    • 3 types of CPTs

      • –

        Choroid plexus papilloma (CPP) (WHO grade I)

      • –

        Atypical CPP (aCPP) (grade II)

      • –

        Choroid plexus carcinoma (CPCa) (grade III)

Imaging

  • Classic: Child with enhancing lobulated (cauliflower-like) mass in atrium of lateral ventricle

  • CPPs occur in proportion to amount of choroid plexus

    • 50% in lateral ventricle (usually atrium)

    • 40% in 4th ventricle &/or foramina of Luschka

    • 5% in 3rd ventricle (roof)

  • Hydrocephalus (overproduction, obstructive)

Top Differential Diagnoses

  • aCPP

  • CPCa

  • Physiologic choroid plexus enlargement

  • Choroid plexus xanthogranuloma

  • Meningioma

  • Intraventricular metastasis

  • Medulloblastoma

  • Ependymoma

Clinical Issues

  • Most common brain tumor in children < 1 year old

    • 13.1% of all brain tumors in 1st year of life

    • 7.9% of fetal brain tumors diagnosed by ultrasound

  • Benign, slowly growing

    • ± cerebrospinal fluid spread (does not distinguish CPP from CPCa)

    • Malignant progression rare

Diagnostic Checklist

  • Consider CPP if intraventricular mass in child < 2 years old

  • Imaging cannot reliably distinguish CPP from aCPP, CPCa

Axial graphic shows a choroid plexus papilloma (CPP) arising from the glomus of the left lateral ventricular trigone. Note the characteristic frond-like surface projections
. CPPs are most common in the lateral ventricles of a child.

Axial NECT in a child with macrocephaly shows hydrocephalus with a lobulated mass
in the atrium of the left lateral ventricle.

Axial T2WI MR in the same patient shows a heterogeneously hyperintense lateral ventricle mass with scattered hypointense flow voids
, indicating high vascularity. The lobulated nature of the mass is striking.

Axial T1WI C+ MR in the same case shows marked enhancement of the lobular mass with frond-like projections, characteristic of CPP. CPP cannot be reliably differentiated from atypical CPP by conventional imaging alone.

TERMINOLOGY

Abbreviations

  • Choroid plexus tumor (CPT)

    • 3 recognized subtypes of CPTs

      • –

        Choroid plexus papilloma (CPP)

      • –

        Atypical choroid plexus papilloma (aCPP)

      • –

        Choroid plexus carcinoma (CPCa)

Definitions

  • Benign (WHO grade I) papillary neoplasm derived from choroid plexus epithelium

IMAGING

General Features

  • Best diagnostic clue

    • Child with strongly enhancing lobulated (cauliflower-like) intraventricular mass

  • Location

    • CPPs occur in proportion to amount of normally present choroid plexus

      • –

        50% → atrium of lateral ventricle, left > right

      • –

        40% → 4th ventricle (posterior medullary velum) and foramina of Luschka

      • –

        5% → 3rd ventricle (roof)

      • –

        5% → multiple sites (synchronous lesions at diagnosis)

      • –

        Rare: Cerebellopontine angle, suprasellar, intraparenchymal

  • Size

    • Varies from tiny to huge

  • Morphology

    • Cauliflower-like mass

Radiographic Findings

  • Radiography

    • Increased cranial-to-facial ratio

    • Sutural diastasis due to hydrocephalus

CT Findings

  • NECT

    • Intraventricular lobular mass

    • 75% iso- or hyperattenuating

    • Ca++ in 25%

    • Hydrocephalus

      • –

        Overproduction of CSF → obstruction

      • –

        Can be as much as 800-1,500 mL/day

  • CECT

    • Intense, homogeneous enhancement

      • –

        Heterogeneous enhancement suggests choroid plexus carcinoma

    • No or minimal parenchymal invasion

    • Rarely, vascular pedicle twists leading to CPP infarction and dense Ca++ (“brain stone”)

  • CTA: Choroidal artery enlargement for lateral ventricular (trigonal) CPPs

MR Findings

  • T1WI

    • Well-delineated iso- to hypointense lobular mass

  • T2WI

    • Iso- to hyperintense mass

    • ± internal linear and branching vascular flow voids

    • Large CPP may bury itself within brain parenchyma

      • –

        Extensive invasion suggests CPCa

    • Hydrocephalus common

  • FLAIR

    • Bright periventricular signal

      • –

        Periventricular interstitial edema due to ventricular obstruction common

      • –

        Asymmetric ipsilateral T2 hyperintensity may suggest invasion and CPCa

  • T2* GRE

    • ± foci of diminished signal if Ca++ &/or blood products are present

  • T1WI C+

    • Robust homogeneous enhancement

    • Occasional cysts and small foci of necrosis

    • Look for CSF dissemination

  • MRA

    • Flow-related signal within mass

    • Enlarged choroidal artery (trigonal mass)

  • MRS

    • NAA absent, mild ↑ choline, lactate if necrotic

    • Myoinositol (mI) elevation in CPP may help to distinguish from CPCa

Ultrasonographic Findings

  • Grayscale ultrasound

    • Hyperechoic mass with frond-like projections

    • Mass echogenicity similar to normal choroid plexus

    • Hydrocephalus

  • Pulsed Doppler

    • Vascular pedicle and internal sampling of mass

      • –

        Bidirectional flow through diastole

      • –

        Arterial tracing shows low impedance

  • Color Doppler

    • Hypervascular mass with bidirectional flow

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