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COEXISTENCE OF CEREBELLAR PRIMITIVE NEUROECTODERMAL TUMOR AND CEREBELLAR DYSPLASIA: Case Report
Venita Jay, MD, FRCPC Children-University of Toronto, Toronto, Ontario, Canada
Department of Pathology, The Hospital for Sick
It has been speculated that the cerebellar primitive neuroectodermal tumor (PNET) in part recapitulates stages in the maturation of normal human neuroblasts. One theoly suggests that these tumors may arise from “primitive cells” or “remnants” of the external granular layer of the cerebellum, which forms a subpial, prolifieratiue zone that gzues rise to neurons of the internal granular layer and stellate and basket cells. I n the pre.rent report, the coexistence of marked cerebellar cortical disorganization and cerebellar PNET is described i n a I-year-old boy. The abnormal dysplastic cortex was in close proximity as well as contiguous to the tumor. Although minor degrees of cerebellar dysplasin may be found incidentally, the coexistence of a severe malformative process contiguous to cerebellar PNET merits the consideration of a possible pathogenetic association between aberrant neuronal migration or maturation and the deuelop- ment of P N W i n this patient.
Keywords brain, cerebellum, dysplasia, medulloblastoma, pathology, primitive neuroec- toderinal tumor
There has been speculation about the contributory role of the rem- nants of primitive neuroectodermal cells in the cerebellum to the origin of the cerebellar primitive neuroectodermal tumor (PNET or medulloblas- toma) [l]. Attention has been drawn to the fetal external granular layer (EGL) of cerebellum, which forms a subpial, proliferative zone that gives rise to neurons of the internal granular layer and stellate and basket cells [2,3]. I t has also been suggested that the cerebellar PNET in part recapitu- lates stages in the maturation of normal neuroblasts [4, 51. In the present report an extraordinary association, that is, coexistence of cerebellar dysplasia and cerebellar PNET, is described.
- Received 15 August 1995; accepted 27 December 1995. The author acknowledges the photographic assistance of Atny Mercer-Connolly. Dr. Maria Zielenska
kindly provided data on polymerase chain reaction analysis. Addresscorrespondence toVenitaJay, MD, DepartmentofPathology, The Hospital for Sick Children,
555 University Avenue, Toronto M5G 1x8, Ontario, CANADA.
Pediatric Pathology U Labomtoly Medicine, 16837-843, 1996 Copyright 0 I996 Taylor U Francis 1077-1O42/96$12.00+ .OO 837
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838 V. JAY
REPORT OF A CASE
Clinical Summary
The patient was a l-year-old East Indian male who was admitted for investigation of irritability, expanding head size, and regression from estab- lished developmental milestones of 6 weeks duration. He had always been thought to have a large head, but exact head size measurements had not been recorded systematically prior to this admission. On examination, findings included a head circumference over the 98th centile, “crackpot” sound on skull percussion, truncal ataxia, meningismus, and a left abducens palsy. The brain computed tomographic (CT) and magnetic resonance imaging (MRI) scans revealed a large posterior fossa tumor, partially cystic and occupying the midline of the cerebellum and the cavity of the fourth ventricle with marked proximal hydrocephalus. There was no suggestion of a gross cerebel- lar or cerebral malformation by radiographic studies.
The patient underwent tumor excision through a suboccipital craniot- omy with insertion of an external ventricular drain. The tumor was dis- crete, grayish, and firm and arising in the vermis. As the postoperative CT scan showed a small amount of residual tumor in the medial left cerebel- lum, this was removed 1 week subsequently followed by ventriculoperi- toneal shunt insertion.
The patient received 11 cycles of ICE chemotherapy (ifosfamide, VP16, carboplatinum) and returned to his developmental level prior to his admis- sion. He was readmitted 11 months later with increasing somnolence and irritability, left-sided ptosis, right-sided tremor, and lethargy. A CT scan showed extensive recurrence of tumor at the original site, as well as the brain stem, posterior third ventricle, ependyma of the lateral ventricles, and subarachnoid space in the posterior fossa. The subsequent course was marked by episodes of respiratory distress, and the child died 1 month after admission. No autopsy was performed.
Materials and Methods and Pathological Findings
Similar pathology was encountered in both surgical resections. Multiple firm tan fragments measuring up to 6 x 5 x 3 cm were received and were submitted for frozen sections, paraffin embedding and histology, immu- nohistochemistry, electron microscopy, flow cytometry, and molecular ge- netic analysis for MYCN oncogene amplification as previously described [ 6, 71. Grossly both tumor and cerebellar cortical tissue were identifiable. Immu- nohistochemical staining was performed by the avidin-biotin complex or peroxidase-antiperoxidase technique using the following an tibodies: glial
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COEXISTENCE OF CEREBELLAR PNET AND DYSPLASIA 839
fibrillary acidic protein (GFAP, polyclonal, 1:200, DAKO) , synaptophysin (monoclonal, 1:5, Behring) , nonphosphorylated neurofilaments (mono- clonal, 1:50, SANBIO), phosphorylated neurofilaments (monoclonal, 1:100, Sternberger-Meyer Immunocytochemicals) , neuron-specific enolase (NSE, polyclonal, 1:250, DAKO), $100 protein (polyclonal, 1:200, DAKO), desmin (monoclonal, 1:20, DAKO), bcl-2 (monoclonal, 1:20, DAKO), nestin (poly- clonal, 1:1000, generous gift from Dr. U. Lendahl), MIB-1 (monoclonal, 1:50, Immunotech), and the p53 DO7 antibody (monoclonal, 1:100, Novocastra).
The tumor showed typical features of a “desmoplastic” medulloblastoma with intense reticulin deposition in the tumor. There was a dimorphous appearance with relatively undifferentiated tumor cells surrounded by abun- dant reticulin and reticulin-free nodules and islands where tumor cells had more abundant cytoplasm, neuropil-like fibrillary stroma, clear cytoplasm, and larger, more vesicular nuclei (Figure 1) . Scattered tumor cells showed SlOO and GFAP positivity. There was prominent synaptophysin and NSE positivity. Staining for desmin was negative. The tumor showed scattered positivity for nonphosphorylated neurofilaments and no staining for phos-
Figure 1. Desnioplastic medulloblastoma showing tumor cells invested by reticulin fibers and a reticulin- free island with neuropil-like stroma. H & E ~ 2 8 0 .
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phorylatedneurofilaments (68, 160,200 subsets). The MIB-1 labeling index in the tumor was 57%.
There was extensive disorganization of the surrounding cerebellar cortex (Figure 2A), both in continuity with the tumor and adjacent to the tumor. There was fusion of adjacent folia, marked disorganization of Purkinje and granular cell layer, numerous dystrophic axons and torpedoes, and dys- trophic calcification. There was no evidence of persistence of the EGL. At the interface between the dysplastic cerebellum and tumor, the tumor cells often aligned around vessels. Neurons in the dysplastic cerebellar cortex showed abnormal synaptophysin staining, both perisomatic and intracytoplasmic (Figure 2B), and exhibited positivity for nonphosphorylated as well as phos- phorylated neurofilaments (all subsets). The abnormally oriented Purkinje cell processes were highlighted by the Bielschowsky stain and showed accu- mulations of nonphosphorylated and phosphorylated neurofilaments. Many GFAP-positive cell processes radiated in different directions intersecting lobules of disorganized neurons. The MIB-1 labeling index in the foci of dysplasia varied from 5 to 10%. Only a small amount of normal cerebellar tissue was identified.
There was scattered p53 and strong bcl-2 positivity within the tumor with rare p53 and no bcl-2-positivity in the dysplastic cortex. Nestin positivity was found in the disorganized cortex but absent in the tumor.
Electron microscopy showed prominent extracellular collagen deposi- tion and tumor cells with neuritic processes containing microtubules and neurosecretory granules. There were also structures reminiscent of synaptic vesicles.
Flow cytometry showed diploidy with 84% cells in the GOGl phase, 6% in the S phase, and 9% in the G2M phase. Analysis of tumor DNA by the polymerase chain reaction revealed no evidence of MYCN amplification.
DISCUSSION
Cerebellar dysplasias may comprise a number of different abnormalities including displaced collections of haphazardly arranged primitive neuro- ectoderinal cells and various ectopias of neurons of the roof nuclei and Purkinje cells [8, 91. Rorke et al. [9] described compact groups of mature neurons, focal or perivascular immature granule cell collections, poorly organized rests with immature and mature neurons and well-organized cell rests resembling normal cerebellar cortex. Cerebellar dysplasia is a frequent incidental finding and may occur in up to 85% of newborns without other significant developmental abnormality, but it is particularly common in trisomy 13-1 5 and trisomy 18 syndromes [ 2,8]. Cerebellar dysplasia may also persist into adult life.
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COEXISTENCE OF CEREBELLAR PNET AND DYSPLASIA 841
Figure 2. (A) Low-power micrograph showing marked disorganization of cerebellar cortex with poor delineation of folia and haphazardly arranged nests of granule cells and Purkinje cells. H & E x112. (B) lmmunostaining for synaptophysin shows perisomatic as well as intracytoplasmic staining in large neurons in the dysplastic cerebellum (arrow) and granular punctate staining in the neuropil. ~ 2 8 0 . Both reproduced at 73%.
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In the present case, the dysplastic changes were extensive and neurons in the dysplastic cortex showed abnormal accumulations of synaptophysin and neurofilament in the perikarya and cell processes. Many GFAP-positive ir- regularly oriented and tangled radial glia-like processes were found within this disorganized tissue, suggesting a role for abnormality of radial glia in the pathogenesis of this lesion. At the cortex-tumor interface, tumor cells often converged around vessels, analogous to the perivascular germinal rests in dysplastic foci. There was no evidence of a persistent EGL in our patient, either in continuity with the tumor or in relation to the dysplastic foci. There was evidence of proliferative activity in the dysplastic foci with an MIB-1 index of up to 10% in areas.
Although a small focus of cerebellar dysplasia may be an incidental finding in newborn brains, the present case showed more extensive and more widespread disorganization of the cerebellum. Our tumor had the charac- teristic features of a desmoplastic medulloblastoma, a variant more com- monly seen in a more lateral location. In our patient, this tumor was associated with an aggressive clinical course with recurrence within a year despite complete surgical resection and chemotherapy. I t is of interest that although the acute clinical symptoms date back only to about 6 weeks prior to the initial admission, the patient was always considered to have a big head, suggesting that the tumor and the cerebellar abnormality might have been present earlier. As high levels of MYCN occur selectively in the developing brain, Rouah et al. [ lo] suggested a possible relationship between MYCN expression and neuronal differentiation in cerebellar PNETs. In view of the prominent neuronal differentiation and the association with cerebellar dys- plasia, MYCN expression was evaluated but found to be normal in our case. Flow cytometry indicated no evidence of aneuploidy, which is said to be associated with a worse outcome [6].
It is possible that the aberrant persistence of residual germinal cells within the foci of cerebellar dysplasia may provide these cells with an abnormally prolonged “window of vulnerability,” enhancing the potential for neoplastic transformation. The expression of nestin, an intermediate filament protein expressed in neuroepithelial progenitor cells [5, 81, was evaluated and was found to be positive in the dysplastic foci but absent in the tumor. Assessment of the immunohistochemical expression of bcl-2 (inhibitor of apoptosis) and p53 in the tumor versus dysplastic of normal cerebellum revealed p53 and bcl-2 positivity in the tumor, rare p53 positivity and absent bcl-2 staining in the dysplastic cortex, and no staining in the normal cerebellum, suggesting a role for altered expression of these genes.
Trojanowski et al. [4, 51 have presented evidence that subsets of PNET cells partially recapitulate stages in normal maturation of neurons, as evi- denced by the expression of a number of neural markers by tumor cells. It
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COEXISTENCE OF CEREBELLAR PNET AND DYSPLASIA 843
appears that neoplastic cells in cerebellar PNET exhibit one or more molecu- lar defects in the sequence of normal maturational events that enable CNS progenitor cells to exit the cell cycle, become committed to a neuronal lineage, and undergo terminal differentiation into postmitotic neurons. The presence of extensive cerebellar dysplasia directly contiguous to PNET in our case provides further support for the hypothesis that the tumor in our patient arose as a result of abnormal genetic control in the migration and differen- tiation of neuronal precursors. This observation is of further interest in view of documented examples of congenital cerebellar PNETs. Although specula- tive, in view of the associated cerebellar dysplasia, young age of our patient, and evidence of big head size even before clinical presentation, it is possible that an aberration of neuronal development progressed on the one hand to PNET and on the other hand to more mature cerebellar dysplasia. Of course, it can be argued that such an association may simply be coincidental, as cerebellar dysplasia is commonly seen as an incidental finding, although the extent of cerebellar disorganization with transitional areas from dysplasia to neoplasia is striking.
REFERENCES
1. Kadin ME, Rubinstein LJ, Nelson JS. Neonatal cerebellar medulloblastonia originating from the fetal external granular layer. J Neuropathol Exp Neurol 1970;29:583-600.
2. Friede RL. Gross and microscopic development of the central nervous system. In: Friede RL, ed. Developmental Neuropathology. 2nd ed. New York: Springer-Verlag, 1989;2-20.
3. Kakic P, Sidnian RL. Histogenesis of the cortical layers in human cerebellum, particularly in the lamina dissecans. J Comp Neurol 1970;139:473-500.
4. Trojanoivski 1% Tohyama T, Lee VM-Y. Medullohlastomas and related primitive neuroectodermal brain tumors of childhood recapitulate molecular milestones in the maturation of neuroblaso. Mol Chem Neuropathol 1992;17: 121-35.
5. Trojanowski JQ Fung K-M, Rorke LB, Tohyama T, ydchnis AT, Lee VM-Y. I n vivo and in vitro models of medulloblastom nd other primitive neuroectodermal brain tumors of childhood. Mol Chem Neuropathol 1994;2 I :219-39.
6. Jay V, Parkinson D, Becker L, Chan F-M’. Cell kinetic analysis in pediatric brain and spinal tumors: A study of 11 7 cases with Ki-67 quantitation and flow cytomeuy. Pediatr Pathol 1994;14:25.3-76.
7. Jay V, SquireJ, Zielenska M, Gerrie B, Humphreys R. Molecular and cytogenetic analysis of a cerebellar primitive neuroectodermal tumor with prominent neuronal differentiation: Detection of MYCN amplification by differential polymerase chain reaction and Southern blot analysis. Pediatr Pathol 1995;15:733-44.
8. Yachnis AT, Rorke LB, Trojanowski JQ. Cerebellar dysplasias in humans: Development and possible relationship to glial and primitive neuroectodermal tumors of the cerebellar vermis. J Neuropathol Exp Neurol 1994;53:61-71.
9. Rorke LB, Fogelson MH, Eggs HE. Cerebellar heterotopia in infancy. Dev Med Child Neurol1968;lO: 644-50.
10. Rouah E, Wilson DR, Armstrong DL, Darlington GJ. N-mycamplification and neuronal differentiation in human primitive neuroectodermal tumors of the central nervous system. Cancer Kes 1989; 493 797-1 801.
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