Brain Tumor Pathol (2002) 19:97-100

9 The Japan Society of Brain Tumor Pathology 2002

Ozlem Kurtkaya-Yapicier 9 Ilhan Elmaci 9 Burak Boran
T i i r k e r Kili~ 9 A y d m Sav 9 M . N e c m e t t i n P a m i r

Dysembryoplastic neuroepithelial tumor of the midbrain tectum:
a case report

Received: April 5, 2002 / Accepted: April 22, 2002
Abstract Dysembryoplastic neuroepithelial tumor (DNT)

is a relatively new nosologic entity. First described in 1988,
it is now included in the " n e u r o n a l and mixed neuronal-glial
turnouts" category in the revised 2000 W o r l d H e a l t h Organization ( W H O ) Classification of T u m o u r s of the Nervous
System. T h e collective experience of m o r e than 300 rep o r t e d cases indicates that, with only rare exceptions, D N T s
are c e r e b r a l cortical lesions. A t present, the actual incidence of extracortical D N T is unknown. W e describe, the
clinicopathologic features of the first tectal D N T . T h e patient was a 51-year-old m a n with a 2-month history of
pulsatile headaches. O n neurologic examination, the only
a b n o r m a l i t y was gait ataxia. Magnetic resonance imaging
( M R I ) d e m o n s t r a t e d a m i d b r a i n t u m o r involving the
tectum. It was hypointense on T l - w e i g h t e d images and
f e a t u r e d an iso- to h y p e r i n t e n s e nodule at its center. The
nodule showed e n h a n c e m e n t u p o n contrast administration.
N o a q u e d u c t a l obstruction or intraventricular extension
of t u m o r was detected. T h e t u m o r was a p p r o a c h e d supratentorially and r e m o v e d completely. The mucoid t u m o r
was well d e m a r c a t e d from neural tissue. H i s t o p a t h o l o g i cally, it was a typical D N T , exhibiting a n o d u l a r p a t t e r n of
growth with a "specific glioneuronal c o m p o n e n t . " This case
r e p o r t documents the first D N T to arise in the m i d b r a i n
tectum and focuses on the p r o b l e m of diagnosing this unc o m m o n t u m o r at extracortical sites.
words Dysembryoplastic
neuroepithelial tumor
( D N T ) 9 Extracortical D N T 9 M i d b r a i n 9 N e u r o i m a g i n g 9
Tectum
Key

Introduction
D y s e m b r y o p l a s t i c n e u r o e p i t h e l i a l t u m o r ( D N T ) is now a
well-known clinicopathologic entity. It is i n t r o d u c e d in the
1993 version of the W H O Classification of Central Nervous
System T u m o u r s 1 and has r e t a i n e d its place in the 2000
version of the W H O classification as well, 2 where the concept of an extracortical D N T was also introduced. A s originally defined, it is primarily a t e m p o r a l lobe lesion of young
adults with longstanding p a r t i a l - c o m p l e x seizures. Years
before the initial description of D N T , C a v a n a g h r e p o r t e d a
h e t e r o g e n o u s group of "small tumors," p r o b a b l y n e u r o n a l
in nature but resembling oligodendroglia, in similar patients. 3 M o r e than 300 cases of D N T have b e e n r e p o r t e d
since the original description of 39 cases by D a u m a s - D u p o r t
et a l . 4
In almost all cases, D N T s originate in the c e r e b r a l
cortex, mainly the mesial t e m p o r a l lobe. 1'4-~4O n l y a handful
of r e p o r t e d cases have b e e n shown to arise at o t h e r
sites, including the cerebellum, ~5'~6 the c e r e b e l l u m and
brainstem, 17 and the caudate n u c l e u s ) 8 Particularly rare are
m o r e sizable lesions involving not only a t e m p o r a l lobe,
but the h y p o t h a l a m u s and basal ganglia as well. 19 T h e association with cortical dysplasia 4 and occasionally with a
well-recognized m a l f o r m a t i o n (the A r n o l d - C h i a r i malformation) 16 raises the question of w h e t h e r D N T s are congenital, quasimalformative lesions r a t h e r than true neoplasms.
W e r e p o r t the first case of extracortical D N T arising from
the m i d b r a i n rectum.

Case report

O. Kurtkaya-Yapicier ( ~ ) 9I. Elmaci 9B. Boran 9T. Kiliq A. Say 9M.N. Pamir
Departments of Neurosurgery and Neuropathology, Marmara
University, PK 53, 81532, Basibiiyfik-Maltepe, Istanbul, Turkey
Tel. +90-216-399-5326; Fax +90-216-305-7961
e-mail: ozlemky@yahoo.com

T h e patient was a 51-year-old m a n with a 2-month history
of pulsatile headache. E x a m i n a t i o n disclosed no sensorimotor deficits or cranial nerve abnormalities. D e e p t e n d o n
reflexes were normal. The only neurologic sign was gait
ataxia. Magnetic resonance imaging ( M R I ) r e v e a l e d a midbrain mass c e n t e r e d on the tectum and expanding the left

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Fig. 1. Tl-weighted magnetic resonance imaging (MRI)shows a tectal Fig. 3. T2-weighted MRI shows a hyperintense lesion, which has a
mass with a hyperintense nodule in the center of it
nodule in the center of it

Fig. 4. Typicalnodular structure of the lesion. Hematoxylinand eosin.
•

Fig. 2. After contrast administration, the nodule shows minimal
enhancement

cerebral peduncle into the cistern. On Tl-weighted images,
it was hypointense with an iso- to hyperintense nodule at its
center (Fig. 1). After contrast administration, only the nodule showed minimal enhancement (Fig. 2). On T2-weighted
images, the overall lesion was hyperintense, the nodule being hypointense. No peritumoral edema or hydrocephalus
was noted (Fig. 3). An occipital craniotomy was performed.
A supratentorial-posterior interhemispheric approach to
the tumor was taken. It was gray and mucoid in character
and separated easily from the surrounding midbrain tissue.
A gross total removal was achieved. The specimen was fixed

in 10% buffered formalin, routinely processed, and embedded in paraffin. Five-micron sections were stained with the
hematoxylin and eosin (H&E) and Alcian blue methods.
With the use of the streptavidin-biotin peroxidase complex (ABC) method, sections were immunostained for
synaptophysin (Biogenex, San Ramon, CA, USA; monoclonal, Clone SNP88, diluted 1:100), glial fibrillary acidic
protein (GFAP) (Biogenex; monoclonal, Clone GA-5,
diluted 1 : 200), vimentin (Biogenex; monoclonal, Clone V9,
diluted 1:500), S-100 protein (Biogenex; monoclonal,
Clone 15E2E2, diluted 1:500), neuron filament protein
(NFP) (Biogenex; clone 2NE14, diluted 1:100), and Ki67
(Biogenex, CloneMIB1, diluted 1:400).
Microscopically, the tumor exhibited a nodular architecture (Fig. 4), the nodules being rich in Alcian blue-positive
mucopolysaccharide. The principal cell type resembled

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Fig. 5. Columns of oligodendroglia-like cells within the nodule with a
large normal-appearing neuron that shows cytoplasmic immunopositivity. Synaptophysin. •

well-differentiated oligodendroglia and was strongly
S-100 protein immunoreactive but lacked staining for
synaptophysin. Some of the neurons within the lesion appeared to float within mucous pools. Perineuronal satellitosis was not seen. Neurons revealed immunopositivity for
synaptophysin, with a largely cytoplasmic pattern of staining (Fig. 5). Stains for neurofilament protein (NFP) showed
the oligodendrocyte-like cells to be aligned along axons.
A positive reaction for glial fibrillary acidic protein (GFAP)
was seen only in scattered reactive astrocytes. There was
no immunoreactivity for G F A P in the tumor cells. No
immunopositivity for Ki67 was noted. The features were
those of an extracortical DNT.
An MRI scan in the immediate postoperative period
showed that the tumor had been totally excised. When discharged 1 week after the surgery, the patient had neither
gait ataxia nor other neurologic abnormalities. A follow-up
MRI scan 36 months after revealed neither residual nor
recurrent tumor (Fig. 6). The patient noted only rare
headaches. Again, the neurologic examination was normal.

Discussion
As originally defined, 3 dysembryoplastic neuroepithelial tumor (DNT) was a benign cerebral lesion, primarily situated
in the temporal lobe. Nearly all are intracortical, with little
white matter involvement. Although extracerebral examples have been reported, to date none have been found
to occur in the midbrain tectum. The cellular derivation of
DNT at this location poses a problem. In keeping with the
original hypothesis 4 that DNTs are derived from secondary
germinal layers, most reported DNTs are supratentorial
and intracortical. As such, they may well originate from the
external cortical layer (subpial granular layer). 4 Leung et
al., in their report of a cerebellar DNT, postulated an origin
from the external granular layer of the cerebellum. 19 Not
surprisingly, Cervera-Pierot et al. in their report of four

Fig. 6. Follow-up MRI shows no mass

caudate nucleus examples suggested a derivation from the
subependymal plate, is A similar explanation may be applied to our case, in that this midbrain example can be
viewed as having a periventricular origin, referring to that
time in development when embryonic cellular migrations
take place.
The second issue that this case report raises is the
difficulty inherent in making a diagnosis of D N T at
extraneocortical sites. The original definition of D N T
leaned heavily upon correlation of morphology with clinical
and neuroimaging data. The 39 lesions occurred in young
patients (under age 20), nearly all with temporal lobe
lesions, who had a longstanding history of seizures (approximately 10 years' duration), specifically of the partial
complex type. Not surprisingly, histologically classic DNTs
occurring at other cerebral cortical sites may present later in
life and with entirely different symptoms. In such cases,
radiographic localization to the cortex and morphologic
data are of great importance. The qualifying clinicopathologic parameters noted above are of even greater importance when making the diagnosis of so-called nonspecific
DNT. The latter is a cerebral cortical lesion but one lacking
typical morphologic features, such as nodules, specific component, "floating neurons," and so forth. At extracortical
sites, clinical and radiographic parameters are of little help.
The diagnosis is necessarily based on finding the classic
morphologic features originally described by DaumasDuport et a l . 4 Such is the case in our patient, who had a late
presentation and, given the location of the tumor, symptoms unrelated to seizures.
In our case, only the histopathological identification of
nodules and the specific columnar glioneuronal element
with accompanying "floating neurons" confirmed the diagnosis of DNT. The principal differential diagnosis of D N T is
oligodendroglioma. Although vague nodule formation may

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be a feature of oligodendroglioma, these are not of the
patterned type, as seen in DNT. Furthermore, oligodendrogliomas usually have more of a tendency toward white matter involvement, perineuronal satellitosis, greater cytologic
atypia, and more frequent proliferative activity; low MIB-1
staining index was seen in only half of DNTs in the large
series of Damaus-Duport et al. 2~
At the present time, the actual incidence of extraneocortical DNTs is unclear. This is due, in part, 1o a lack of
precise diagnostic criteria for DNTs occurring at unusual
sites where the anatomic substrate affecting their morphology differs from that of cerebral cortex, and the everincreasing spectrum of "odd" glioneuronal tumors composed in part of oligodendrocyte-like cells. 21 Although
the indolent clinical behavior of these lesions and DNTs
makes their distinction of little clinical importance, their
collective distinction from oligodendroglioma, a proliferative, infiltrative glioma, remains essential.
In summary, extraneocortical DNTs may be more common than suspected, and their sites of origin continue to
expand. Although differing in clinical presentation from
classic, supratentorial DNTs, they appear to pursue a similar benign course.

Acknowledgment We are greatly indebted to Prof. Dr. Bernd W.
Scheithauer for his review.

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