The Usefulness of MR Imaging in the Diagnosis of Dysembryoplastic Neuroepithelial Tumor in Children: A Study of 14 Cases

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The Usefulness of MR Imaging in the Diagnosis of Dysembryoplastic Neuroepithelial Tumor in Children: A Study of 14 Cases
  The Usefulness of MR Imaging in the Diagnosisof Dysembryoplastic Neuroepithelial Tumor inChildren: A Study of 14 Cases Carla Fernandez, Nadine Girard, Armando Paz Paredes, Corinne Bouvier-Labit,Gabriel Lena, and Dominique Figarella-Branger  BACKGROUND AND PURPOSE:  Dysembryoplastic neuroepithelial tumors (DNTs) are be-nign lesions affecting children and are associated with epilepsy. The goal of our study was tobetter characterize the clinical-radiologic-pathologic spectrum of DNTs (complex and simpleforms only) in a series of 14 children.  METHODS:  Clinical, neuroradiologic, and pathologic features of all cases were retrospec-tively studied.  RESULTS:  Eleven cases of complex and three cases of simple DNTs were identified. Meanfollow-up was 87 months, and no recurrence was recorded except for one case of simple DNT. We found that some neuroradiologic features may be helpful to support the diagnosis of DNT:presence of “septations,” triangular pattern of distribution, and absence of contrast enhance-ment. CONCLUSION:  The evidence of the specific glioneuronal element is found by pathologicexamination, but the typical neuroradiologic aspect of DNT suggests this diagnosis preopera-tively. Radiologic examination may be helpful for the diagnosis of DNT when pathologicfindings are inconclusive. First described in 1988 by C. Daumas-Duport (1),dysembryoplastic neuroepithelial tumors (DNTs) arebenign lesions affecting young people and are clini-cally characterized by drug-resistant partial seizuresand normal neurologic examination. Neuroimagingtypically shows a predominantly cortical and well-demarcated lesion (1, 2). Most DNTs do not displaycontrast enhancement (1, 3–6). Three histologicforms have been described (3, 7). The complex formis characterized by the association of a specific glio-neuronal element (SGNE) with glial nodules and amultinodular architecture. Foci of cortical dysplasiaare common. The simple form demonstrates only theSGNE (7). A third, “nonspecific,” form of DNT doesnot show the SGNE but displays the same clinical andneuroimaging features as complex DNT (3). Onpathologic examination, this form may mimic anykind of glioma and, consequently, its existence isdebated. Daumas-Duport et al define the clinical-radiologic criteria of DNT as follows: 1) partial sei-zures, with or without secondary generalization, be-ginning before the age of 20 years, 2) no neurologicdeficit or stable congenital deficit, 3) cortical locationof the lesion as best demonstrated by MR imaging,and 4) neither mass effect nor peritumoral edemafindings at imaging (3).We report a series of 14 DNTs (with SGNE) inchildren. Clinical, neuroradiologic, and pathologic re-sults were reviewed, and we found that additionalneuroradiologic findings were helpful to perform thediagnosis of DNT. To date, all children are alive, inkeeping with the benign clinical course of DNT. Methods Case Selection and Clinical Findings Between 1986 and 2000, 14 typical DNTs were diagnosed inchildren at our institution on the basis of pathologic findings. All patients fulfilled the clinical-radiologic criteria defined byDaumas-Duport et al. Age at diagnosis, sex, symptom durationbefore surgical excision, and clinical presentation, including thetype of epilepsy, were recorded. Type of resection (tumorec-tomy vs lobectomy) and extent of resection were defined on thebasis of both postoperative reports and early postoperative Received October 10, 2002; accepted after revision, December16.Supported by the Association pour la Recherche contre le Can-cer, the Groupement des Entreprises Franc¸aises dans la Luttecontre le Cancer, and institutional grants to D.F.B.From the Department of Pathology and Neuropathology (C.F.,C.B.-L., D.F.-B.); Department of Neuroradiology (N.G.); and De-partment of Pediatric Neurosurgery, Hoˆpital d’Enfants de laTimone (A.P.P, G.L.), Marseille, France Address correspondence to Dominique Figarella-Branger, Ser- vice d’Anatomie Pathologique et Neuropathologie, Hoˆpital de laTimone, 264 rue Saint-Pierre, 13385 Marseille Cedex 05, France. ©  American Society of Neuroradiology  AJNR Am J Neuroradiol  24:829–834, May 2003829  imaging. At the time of the last medical examination or on thebasis of information obtained from a questionnaire sent to thepatients ’  medical doctors, the following parameters were re-corded: anticonvulsive treatment (yes-no), seizure frequency,and recurrence (yes-no).  Neuroimaging  Preoperative and postoperative neuroradiologic examina-tions were reviewed by a neuroradiologist (N.G.). A preoper-ative CT scan was available in eight cases, and an iodinatedcontrast media injection was done in six cases. PreoperativeMR imaging findings were available in all cases, with gadolin-ium injection in 10 cases. Lesion location, white matter involve-ment, calcifications, cystic component, overlying skull deforma-tion, contrast enhancement, lesion shape, and presence of  “ septations ”  were studied.  Pathologic Analysis Surgical specimens were fixed in formalin or Bouin ’ s fixativeand paraffin embedded. In each case, all available microscopicslides were reviewed by two pathologists (D.F.B. and C.F.).Glial cell type, the presence of anaplasia criteria (includingatypias, mitosis, necrosis, and endothelial proliferation), dys-plastic neurons, perivascular inflammation, white matter, andmeningeal involvement were studied. Results Clinical Features The age at surgery ranged from 3 to 18 years(mean, 10.1 years). Nine male and five female pa-tients were included in the study. Partial seizuresoccurred in all cases and were subsequently general-ized in seven cases (cases 3, 5, 6, 8, 10, 12, and 14).Seizures were drug-resistant in nine cases. Seizureduration ranged from 2 weeks to 14 years, with amean duration of 36 months before surgery. Thirteenpatients had no neurologic deficit, and one patient(case 8) had a congenital unilateral sensorimotor def-icit that remained unchanged for 4 years. Three pa-tients presented with behavior disorders (cases 2, 5,and 8) and two with mental retardation (cases 8 and9). Total surgical excision (tumorectomy [cases 1 – 5and 7 – 14] or lobectomy [case 6]) was performed andno adjuvant therapy was administered (Table 1).  Neuroimaging   All cases displayed a cortical tumoral lesion thatdemonstrated neither perilesional edema nor masseffect on midline structures (Table 2, Figs 1A  – D and2A  – D). Temporal, frontal, parietal, and occipitallobes were involved in six, seven, one, and one cases,respectively. One case (case 8) involved two adjacentlobes. On CT scans, the lesion appeared hypoattenu-ated in seven of eight available cases and heteroge-neous in one case. No case demonstrated calcifica-tion, and two cases showed small cysts (cases 7 and 8).On T1-weighted images (Fig 1A), the lesion appearedto be hypointense in 13 cases and heterogeneous inone case (case 7). On T2-weighted images (Fig 1B),the lesion was of high signal intensity in all cases. A deformation of the overlying skull was observed in six cases. Gadolinium injection induced a tumor en-hancement in three of 10 available cases, always witha nodular pattern. One of these cases had major hem-orrhagic changes (case 7; Fig 2). In all cases, the lesionexceeded the thickness of the normal cortex and in- volved the white matter. In eight cases, the tumor width was maximal at the cortical level and decreased towardtheventricles,leadingtoatriangularpattern(Fig1D)of distribution usually best seen on coronal images. Thetumor boundaries were also rectilinear in three othercases but with a rectangular pattern (Fig 1C) of distri-bution, whereas the three remaining lesions wererounded. In all but two cases (cases 9 and 11), the lesionseemed to be divided by thin septa (Fig 1A-C). Thesesepta were best seen on high-resolution MR images(inversion recovery 3-mm-thick sections, 3D T1- weighted images of 1-mm-thick sections) and had the TABLE 1: Clinical findings Patient(no.) Age(y)/Sex SymptomDurationSeizureTypeExtent of ResectionType of ResectionSeizure Frequency atLast MedicalExamination/  AnticonvulsiveTreatmentTumorRecurrenceFollow-up(Months)1 11/M 7 months Partial* Total Tumorectomy 0/No No 912 15/M 4 years Partial* Total Tumorectomy 0/No No 1483 7/M 9 months Partial* Total Tumorectomy 0/No No 1654 14/M 6 months Partial Total Tumorectomy 0/No No 295 9/F 8 months Partial Total Tumorectomy 0/Yes No 326 9/M 2 years Partial* Total Lobectomy 0/No No 637 12/F 9 months Partial Total Tumorectomy 0/No No 258 4/F 3 years Partial* Total Tumorectomy 0/No No 999 11/F 7 years Partial* Total Tumorectomy 0/No No 8710 8/M 4 months Partial Total Tumorectomy Unchanged/yes No 3611 3/M 5 months Partial* Total Tumorectomy 0/Yes No 3612 18/F 14 years Partial* Total Tumorectomy 0/No No 16713 6/M 2 years Partial* Total Tumorectomy 0 then recurrence/yes Yes 12514 14/M 2 weeks Partial Total Tumorectomy 0/No No 117* Drug-resistant seizures. 830 FERNANDEZ AJNR: 24, May 2003  F IG  1. Typical DNT findings.  A,  Sagittal T1-weighted MR imageshows a large lesion of low signal in-tensity involving the temporal lobe,without edema or mass effect and cor-responding to a complex form of DNT.The lesion is divided by septationsleading to an alveolar aspect. B,  The lesion is of high signal inten-sity on this T2-weighted MR image.The septations appear to be of lowsignal intensity. C,  Sagittal T1-weighted MR imageshows a frontoparietal DNT with sharpboundaries and a rectangular patternof distribution. D,  Coronal T2-weighted MR imageillustrates the triangular pattern of distri-butiontypicalofDNT,withatumorwidththat is maximal at the cortical level anddecreases toward brain ventricles. E,  Low-magnification view showingthe cortical location and the nodular ar-chitecture typical of DNT (hematoxylinphloxin-saffron, magnification  10). F, Theglio-neuronalspecificelementis composed of oligodendrocyte-likecells surrounding areas of mucoid sub-stance containing “floating neurons”(hematoxylin phloxin-saffron, magnifi-cation  300). TABLE 2: Neuroradiologic findings Patient(no.) LocationCT MRDistribution Septations Skull Erosion Attenuation Contrast T1/T2 Contrast1 Frontal Hypoattenuated NA   2  /  1    Rectangular    2 Temporal NA NA   2  /  1    Triangular    3 Temporal Hypoattenuated    2  /  1  NA Triangular    4 Frontal Hypoattenuated    2  /  1    Rectangular    5 Temporal NA NA   2  /  1  Nodular Round    6 Temporal Hypoattenuated    2  /  1  NA Triangular    7 Occipital Heterogeneous Nodular H/  1  Nodular Triangular    8 Frontoparietal NA NA   2  /  1  Nodular Rectangular    9 Temporal NA NA   2  /  1    Triangular    10 Frontal Hypoattenuated    2  /  1  NA Triangular    11 Temporal NA NA   2  /  1    Triangular    12 Frontal NA NA   2  /  1    Triangular    13 Frontal Hypoattenuated    2  /  1  NA Round    14 Frontal Hypoattenuated    2  /  1    Round    Note. — NA, not available; MRI, T1/T2  T1-weighted image/T2-weighted image; 2 , hypointense lesion; 1 , hyperintense lesion; H, heterogeneouslesion;  , negative;  , positive.  AJNR: 24, May 2003 DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR 831  same intensity as normal cortex. We named them  “ sep-tations. ”  Consequently, most lesions were well-demar-cated triangular lesions (57% of cases), did not displayenhancement after contrast material injection (78% of cases), and showed septations (85% of cases). The as-sociation of these three features was observed in five(36%) of 14 cases.  Histologic Findings  A typical specific SGNE was clearly identifiable inall cases (Fig1E and F). In three cases (cases 12, 13,and 14), the SGNE represented the whole lesion,leading to the diagnosis of the simple form of DNT(Table 3). The 11 other cases displayed glial nodulesand were classified as complex DNTs. In these glialnodules, oligodendrocyte-like areas were observed inall cases, associated with piloid cells in two cases andfibrillary astrocytes in one case. Calcifications weredetected in four cases. Nuclear pleiomorphism (Fig2E) was noted in three complex DNTs, including onecase with strong atypias (case 2). Rare mitoses wereobserved in one case (case 2). One case demonstratedscarce endothelial proliferation (case 9). Necrosis wasnot recorded. Discrete and focal perivascular lympho-cytic cuffing was present in three cases (cases 6, 7, and8). One of them (case 7) presented major hemor-rhagic changes (Fig 2F). In six cases, the lesion in- volved the leptomeninges, and the SGNE was occa-sionally observed in this location. Numerous neurons were entrapped in the glial component in all cases, F IG  2. DNT involving the occipital lobe and pre-senting hemorrhagic changes (case 7).  A,  On CT scan, the lesion appears of low at-tenuation and shows a nodular enhancement af-ter contrast injection. B  and  C,  On transverse (  B  ) and sagittal (  C  )T1-weighted MR images, the DNT is of low signalintensity, displays septations, but shows threeareas of hyperintensity after gadolinium injection,mimicking a glioma. D,  Transverse T2-weighted MR image showsthe absence of edema and mass effect on me-dian structure. E,  Marked nuclear atypias can be observed inthe glial areas of DNT (hematoxylin phloxin-saf-fron, magnification  200). F,  An oligodendroglioma-like area showing ma- jor hemorrhagic changes characterized by nu-merous hemosiderin-laden histiocytes (hematox-ylin phloxin-saffron, magnification  200). 832 FERNANDEZ AJNR: 24, May 2003  but no dysplasic neurons typical of gangliogliomas were observed. Cortical dysplasia was observed inseven of eight complex DNTs where enough cortex  was available at pathologic examination.  Follow-up The follow-up duration ranged from 25 to 167months, with a mean of 87 months. At the time of thelast examinations, 12 patients were free of seizures,and only one still used an anticonvulsive treatment.Seizure frequency was unchanged in one case (case10). In the remaining case (case 13), seizures beganagain after a seizure-free period of 2 years, and tumorrecurrence was observed on MR images 125 monthsafter the initial excision. The child underwent surgeryat another center, and we could not study the newpathologic specimen. No neuroradiologic evidence of recurrence was observed in the 13 others cases. Discussion Clinical presentation of DNT is stereotyped: a longhistory of partial drug-resistant seizures and the ab-sence of progressive neurologic deficit (1, 3 – 6).DNTs are stable and benign lesions, although onecase of malignant transformation 11 years after initialexcision has been reported (8). Currently, lesion sta-bility cannot often be evaluated, because the occur-rence of partial seizures leads to neuroimaging andsubsequent surgical excision. Surgical excision re-mains necessary, because it provides the best chanceto cure epilepsy and prevents hemorrhagic complica-tions (9). Regarding our patients, most lesions wereinitially considered as tumors on the basis of neuro-imaging findings, so a simple tumorectomy was per-formed in 13 cases, whereas only one patient under- went classic epilepsy surgery. All but two patients were seizure free after excision, so it seems that tu-morectomy is sufficient to cure epilepsy in most cases.The single case of recurrence (case 12) was initially asimple form of DNT. It is currently the only reportedcase of recurrence except for a case of malignanttransformation (8).Typically, DNTs display hypointensities on T1- weighted MR images and hyperintensities on T2- weighted MR images (3, 4, 10). Edema and masseffect on midline structures are lacking (3, 4, 10),although they may be observed in case of hemor-rhagic complications (9, 11). Diffuse astrocytomasand World Health Organization (WHO) grade IIoligodendrogliomas may in some cases share this neu-roradiologic aspect (12). Nevertheless, it is of theutmost importance to distinguish DNTs from glio-mas, because DNTs can be cured by surgery alone.This is of particular interest in children because of thehighly deleterious effect of adjuvant therapies. Gen-erally, pathologic examination leads to the diagnosisof DNT if the SGNE is present; however, it appearsobvious that this diagnosis must be affirmed cau-tiously, because some oligodendrogliomas harboringcystic changes and entrapping neurons may mimic theSGNE (13). Moreover, the aggressiveness criteria,including mitosis, ischemic necrosis, capillary prolif-eration, nuclear atypias, and meningeal involvementare usually observed in malignant tumors but do notexclude the diagnosis of DNT (1, 3, 5, 6, 14, 15). Forall these reasons, the diagnosis of DNT must be theresult of a multidisciplinary discussion including cli-nicians, neuroradiologists, and pathologists.With regard to our series, neuroimaging findingsseem to be very helpful in the diagnosis of DNT. Inaddition to lack of peritumoral edema and mass effecton midline structures, triangular pattern of distributionand presence of septations are frequently observed. Be-cause DNTs are thought to be of dysembryoplasticsrcin, the triangular pattern of distribution may berelated to the radial glial fibers pathway. Septationsprobably correspond to the lobular aspect describedelsewhere (2). They are true septations and are notcaused by distortions of sulci and reflection. Theymay reflect the nodular architecture of the DNT andthe demarcations between normal cortex, densely cel-lular zones (glial nodules), and loose zones (SGNE). TABLE 3: Pathologic findings PatientCorticalDysplasiaGlial NoduleCell Type Calcifications AtypiasEndothelialProliferationPerivascularInflammationMeningealInvolvement1 C.U.    O       2 M.I. NA O  P       3 R.E.    O       4 S.C.    O       5 D.E. NA O       6 B.E.    O   A        7 B.O.    O  P       8 L.A.    O       9 Z.E.    O       10 A.N. NA O       11 C.H.    O       12 A.Y.    None       13 P.I. NA None       14 C.E. NA None       Note. — O, oligodendrocytes; P, piloid cells; A, fibrillary astrocytes;  , negative;  , positive; NA, not available.  AJNR: 24, May 2003 DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR 833
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