Cas de la semaine #2427 Février 2017

Préparé par Dr Philippe Ouellet R4

Dr Jean-Claude Décarie MD

Hôpital Sainte-Justine

Département de radiologieFaculté de médecine

• Se présente avec fontanelle bombée à l’urgence

• Patiente afébrile

• Aucune information sur le suivi anténatal disponible

2 MoisFontanelle Bombée

Histoire Clinique

Scan cérébral

Sans contraste Avec contraste

IRM avec contrasteT2 FLAIRT2

IRM Post-dérivation ventriculaire

T1 pré contraste T1 C+

Description radiologiqueCT Scan C-/C+• Volumineuse lésion ne respectant

aucun compartiment intracrânien (composantes intra et extra axiales)

• Masse hétérogène avec composantes kystique, solide et calcifiée

• Œdème vasogénique du parenchyme cérébral adjacent

• Important effet de masse entraînant une hydrocéphalie triventriculaire

Description radiologiqueIRM C+

• Volumineuse lésion unique de signal très hétérogèneØComposantes kystiques hyper-

intense T2

ØComposantes solides iso-intense T1/T2 avec rehaussement hétérogène post-gadolinium

ØAbsence de composante graisseuse évidente (hyper-intense T1)

Diagnostic DifférentielVolumineuse masse très hétérogène chez bébé de 2 mois

(lésions découvertes in utero ou dans premiers 3 mois de vie sont considérées congénitales)

ü Tératome Immature

ü Carcinome des Plexus ChoroïdesØ Présentation généralement plus tardive (vers 3 et 5 ans) comparativement

aux papillomes des plexus choroides (habituellement < 1 an - papillomes présentent critères radiologiques moins agressifs).

ü PNET (Primitive Neuro Ectodermal Tumor)Ø Rare, < 5% des tumeurs supra-tentorielles de l’enfant Ø Portion solide peut être hyperdense au CT scan et isointense en T2 dû au haut

ratio noyau/cytoplasme

ü Autres types de Tumeur Germinale

Diagnosticfinal

Tératome Immature

Tératome Intracrânien

• Tumeur cérébrale congénitale la plus fréquente (26,6% à 42%)

• Tumeur embryonnaire formée de cellules pluripotentes

• Formée de trois couches germinales (ectoderme, mésoderme et endoderme) expliquant son apparence très hétérogène

• 2 Types

Ø Tératome Mature: tissu complètement différentiéo Présence de gras suggère diagnostic

Ø Tératome Immature: tissu partiellement ou complètement dédifférencié

Tératome Immature

• Caractéristiques la distinguant des autres néoplasies intracrâniennes chez le nouveau né:ØLésion très agressive avec non respect des compartiments

intracrâniens

ØApparence très hétérogène

• Caractéristiques biochimiquesØAugmentation possible des CEA (carcinoembryonic antigen)

ØAugmentation possible des AFP (alpha-fetoprotein)

• Possibilité de métastases dans le liquide céphalo-rachidien

Tératome immaturePronostic + traitement

Traitement

• Résection Chirurgicale

Pronostic

• Défavorable

• Survie à 5 ans de 18%

types and their mortality rates appear in Table 2. Mostcongenital tumors (about 60%) are supratentorial, arisingfrom the pineal gland, the suprasellar area or the cerebralhemispheres. Macrocephaly is usually the first clinicalfinding. Increased intracranial pressure signs are not oftenobserved because of the great capacity for accommodationto the increased volume in the fetus and in neonates withopened sutures [35]. Intratumoral hemorrhage is relativelycommon, varying between 3 and 18% [38–40].

Teratoma is the most common congenital brain tumorand represents 26.6 to 48% [38–41] (Table 2). Congenitalteratomas are predominantly supratentorial, with the cere-bral hemispheres being the main primary site, followed bythe third ventricle and the pineal region [42]. On ultra-sound, they are seen as typically large, mid-line heteroge-neous tumors with solid areas replacing much of the brain.Cystic components are often found [41] and probablyrepresent necrotic areas in tumors with a rapid growth rate.Calcifications are possible, but unusual.

The astrocytoma is the most common neuroglial tumor.The cerebral hemispheres are the main primary site,followed by the optic nerve, the thalamus and themesencephalus. They typically present with macrocephaly.Fetal ultrasound and MRI show a solid tumor replacing thenormal brain parenchyma. Hemorrhage is common.

The choroid plexus papilloma is composed of matureepithelial cells derived from choroid plexus epithelium. Itpresents clinically as macrocephaly, with rapid onset ofhydrocephalus, secondary to the overproduction and/ormechanical obstruction to cerebrospinal fluid (CSF) circu-lation [1]. These are well defined, intraventricular masses,hyperechoic on ultrasound and mostly hyperattenuating onCT (Fig. 4a, b), with intense contrast enhancement. OnMRI, they present as homogeneous masses on T1-weightedimages, with the central tumor areas hypointense comparedwith grey matter on T2-weighted images [43]. Completesurgical resection is curative, but intraoperative hemorrhageis common and may have serious consequences. Choroidplexus carcinomas are very rare in neonates. They are oftenassociated with marked vasogenic edema and may behyperdense on CT because of the high cellularity.

Primitive neuroectodermal tumors (PNET) (Fig. 4c, d)are small-cell malignant tumors arising from the neuralcrest [40]. The most common locations are the cerebellumand the cerebral hemispheres. Congenital tumors have apoor prognosis as a consequence of the rapid tumor growth,with early extension throughout the CSF pathways.

The diagnosis of fetal and neonatal brain tumors isassociated with high mortality rates (Table 2). Recentadvances in MRI technology include the development ofmagnetic resonance diffusion sequences (DWI), which mayidentify areas of restricted water movement and of magneticresonance spectroscopy (MRS), which recognizes changes inmetabolite concentration [44]. These technical improvementshave opened up exciting perspectives, suggesting thepossibility of differentiating between histological tumortypes [20, 45], but preliminary reports have not yet beenconfirmed for congenital brain tumors. The main role ofimaging studies is still to determine the extent of the tumorin order to evaluate therapy challenges and to identifypotentially curable tumors, such as plexus papillomas,differentiating them from rapidly fatal ones.

Renal tumors

Renal tumors represent 5–7.1% of all congenital tumors(Table 1). They are mostly benign, with the most frequenthistological types being mesoblastic nephroma (MSN),nephroblastomatosis and the multilocular cystic nephroma[14]. Wilms’ tumor and renal rhabdoid tumors are rare inneonates [1, 14, 46].

The MSN represents 66% of all congenital renal tumors[14]. It is a benign hamartomatous tumor, arising fromproliferating nephrogenic mesenchyme. Fetal tumors have aworse prognosis than neonatal ones [14]. They present inutero as large, solid, infiltrative, unilateral renal masses[47], sometimes associated with polyhydramnios. Hyper-calcemia has been described in neonatal cases [1, 3]. Thetumor has variable echogenicity, with homogeneous solidtissue on ultrasound. CT and MRI show a solid, relativelyhomogeneous renal tumor, typically involving the renalsinus and with variable contrast enhancement (Fig. 5a, b).The mass may present cystic and hemorrhagic areas [46].

Nephroblastomatosis consists of diffuse, multifocalnephrogenic rests in the kidneys. It is found incidentallyin 1% of normal children at post-mortem studies and maycause a Wilms’ tumor in 30–40% of the cases (Fig. 5c).There is a well-known association with Beckwith-Wiedemannsyndrome, trisomy 18 and sporadic aniridia [48]. Typicalultrasound images show multifocal, subcapsular renal nod-ules, hypo- or isoechoic, related to renal parenchyma. Thenodules present low attenuation on CT and low signalintensity on both T1- and T2-weighted images on MRI

Table 2 CNS tumors. Histological type and mortality rate of mainCNS tumors [37–41]

CNS tumors % Mortality rate

Intracranial teratomas 26.6–48% 88%

Astrocytomas 7.4–28.8% 64–68%

Choroid plexus papilloma 3.7–13.2% 27%

PNET 3–13% 88%

Craniopharyngioma 5.6–6.8% 76.5%

Ependymoma 4.4% 91%

302 Insights Imaging (2011) 2:297–308

Fréquence et pronostic des tumeurs congénitales du SNC

Tiré de Alamo et al. Insights Imaging 2011

Références 1. Alamo L, Beck-Popovic M, GudinchetF, Meuli R. “Congenital tumors: imaging when life begins”. Insights Imaging 2011; 2(3): 297-308.

2.Woodward PJ, Sohaey R, Kennedy A, Koeller KK. “From the Archives of the AFIP: a comprehensive review of fetal tumors with pathologic correlation”. RadioGraphics 2005; 25(1):215-42.