Primitive supratentorial neuroectodermal tumor in an adult

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<ul><li><p>bone tissue. It was very adherent to the right internal carotidartery and optic nerve, therefore, a subtotal excision was per-formed. On pathological examination, the lesion was composedof interconnecting osteoid islands and highly vascularized stroma.The osteoid tissue was rimmed by osteoblasts. Scattered osteo-clasts and small bony trabeculae were seen. There was no evi-dence of malignancy. The lesion was diagnosed as a benignosteoblastoma (Fig. 3).Post-operative neurological examination revealed no additional</p><p>deficit and there was no neurological progression over 18 years,other than the right eye lateral gaze palsy present preoperatively.There was no evidence of enlargement at 18 years on cranial CTscan and MRI (Figs. 4 and 5).</p><p>DISCUSSION</p><p>Benign osteoblastoma is a rare bone tumor with an indolent bio-logical behavior and good clinical prognosis. It is very rare inthe cranium.5 The temporal bone is the most common site of oste-oblastoma in the neocranium.6 In the reported case, the tumororiginated from the petrous temporal bone and extended to theparasellar region and cavernous sinus.It is important to differentiate osteoblastoma from osteoid oste-</p><p>oma. The pain from osteoid osteoma generally increases noctur-nally and responds to salicylates, while the pain fromosteoblastoma is continuous and does not respond to salicylates.Osteoblastoma has a greater potential to enlarge than osteoid oste-oma and presents by mass effect rather than pain.5,6 In this case,paralysis of the sixth cranial nerve aided localization of the pathol-ogy. Although imaging is insufficient to determine the nature ofthe lesion, it may be highly suggestive.2 However, low-gradechordoma, chondrosarcoma and giant cell tumors also have simi-lar radiological features.2 They present as cortical or medullary,diaphyseal or metaphyseal, prominently radiolucent lesions withvariable calcification and clearly defined, non-lobular margins.2</p><p>Histological diagnosis is important. On microscopic examination,early lesions contain actively propagated connective tissue isletsand older lesions frequently show large foci of ossification. Inall lesions, irregular fibrous stroma and osteoid deposits are seen.Stroma tends to be well vascularized, particularly in early tumorsand rarely exhibits extravasation. Rarely minor atypical changesmay be observed in osteoblast mitochondria.3</p><p>Optimal primary treatment of benign osteoblastoma is totalsurgical excision.7 If, as reported here, the tumor is not suitablefor total surgical excision due to its location, subtotal excision isadequate as the probability of recurrence is low. No progressionhas been observed during 18 years post-operative follow up inthis patient. Therefore, radical surgical excision, which may havesignificant post-operative morbidity and mortality, should beavoided and safer palliative excisions considered. If there isany evidence of malignancy on pathological examination, radio-therapy and chemotherapy may be administered. However, it hasbeen reported that radiotherapy may induce or promote malig-nant degeneration.1,2,3 Hence the role of the radiotherapy iscontroversial.</p><p>REFERENCES</p><p>1. Batay F, Savas A, Ugur HC, Kanpolat Y. Benign osteoblastoma of the orbitalpart of the frontal bone: case report. Acta Neurochir 1998; 140: 729730.</p><p>2. Clutter DJ, Leopold LV. Benign osteoblastoma: report of a case and review ofthe literature. Arch Otolaryngol 1984; 110: 334336.</p><p>3. Lucas DR, Unni KK, McLeod RA, OConnor MI, Sim FH. Osteoblastoma:clinicopathologic study of 306 cases. Hum Pathol 1994; 25: 117134.</p><p>4. Berciano J, Perez JL, Fernandez F. Voluminous benign osteoblastoma of theskull. Surg Neurol 1983; 20: 383386.</p><p>5. Chen K, Weinberg R, Simpson P, Tschang T. Osteoblastoma of the nasal cavity.Laryngol Otol 1993; 107: 737739.</p><p>6. Khasaba A, Donata GD, Vassalo G. Benign osteoblastoma of the mastoid part ofthe temporal bone: case report. J Laryngol Otol 1995; 109: 565568.</p><p>7. Ciappetta P, Salvati M, Raco A, Artico M. Benign osteoblastoma of the sphenoidbone. Neurochirurgica 1991; 34: 97100.</p><p>Primitive supratentorialneuroectodermal tumor in anadult</p><p>AT Kouyialis1 MDMD, EI Boviatsis1 MDMD, IK Karampelas1 MDMD,</p><p>S Korfias1 MDMD, P Korkolopoulou2 MDMD, DE Sakas1 MDMD</p><p>1Department of Neurosurgery, University of Athens Medical School,</p><p>Evangelismos Hospital; 2Department of Pathology, University of Athens</p><p>Medical School; Athens, Greece</p><p>Summary We report the case of a 32-year-old female with a diag-</p><p>nosis of supratentorial tumour. Total removal of the tumour was</p><p>achieved in a two-stage procedure. Histopathology revealed a primi-</p><p>tive neuroectodermal tumour (PNET), an unusual and highly malig-</p><p>nant, mainly infratentorial tumour of childhood that is uncommonly</p><p>described in the supratentorial compartment of adults. We review the</p><p>literature and describe the existing knowledge of these tumours.</p><p> 2005 Elsevier Ltd. All rights reserved.</p><p>Journal of Clinical Neuroscience (2005) 12(4), 492495</p><p>0967-5868/$ - see front matter 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.jocn.2004.07.014</p><p>Keywords: primitive neuroectodermal tumour, supratentorial,</p><p>medulloblastoma, adulthood</p><p>Received 11 February 2004</p><p>Accepted 13 July 2004</p><p>Correspondence to: Efstathios J Boviatsis MD, Department of Neurosurgery,</p><p>Evangelismos General Hospital, 61 ipsilantou Street, Athens 115 21, Greece.</p><p>Tel.: +30 210 7201654; Fax: +30 210 7215281;</p><p>E-mail:</p><p>INTRODUCTION</p><p>The term primitive neuroectodermal tumour (PNET) refers to agroup of neoplasms consisting of highly undifferentiated malignantcells that present mainly in children and histologically resemblecerebellar medulloblastoma. They are chiefly characterised bysmall, round, undifferentiated cells with scanty cytoplasm. Oneof the outstanding features of the malignant character of PNET istheir ability to disseminate within the central nervous system(CNS) via the cerebrospinal fluid (CSF) pathways. Thus, at the timeof diagnosis, multiple foci of disease are frequently discovered.Although this tumour is relatively uncommon, it is well</p><p>recognised, particularly in children, yet there is still ongoingdebate and considerable controversy concerning the histogenesisand classification of PNET. An extensive literature review hasrevealed few reports of PNET in adults.1 In this report, an adultfemale with a supratentorial PNET is described and the existingliterature regarding the unusual features of these tumoursreviewed.</p><p>Journal of Clinical Neuroscience (2005) 12(4) 2005 Elsevier Ltd. All rights reserved.</p><p>492 Kouyialis et al.</p></li><li><p>CASE REPORT</p><p>A 32-year-old woman was admitted complaining of severe morn-ing headaches, recent gait disturbance and fatigue with walkingdue to progressive decline in function of both lower limbs. Neuro-logical examination revealed increased tendon reflexes in theupper and lower limbs with normal muscle power. She had bilat-eral papilledema but no other neurological abnormality. CT andMRI of the brain revealed a large space-occupying lesion in themid- and parasagittal convexity of both hemispheres, just beneaththe calvarium (Fig. 1). The mass consists of three components; thelargest, measuring 5 7 7 cm, was directly under the bone;the other two sections, measuring 4 3 3 cm each, lay withinthe parenchyma, yet had clearly defined borders. Digital substrac-tion angiography (DSA) showed blood supply deriving frombranches of the left external carotid artery and a considerabledownward displacement of the superior sagittal sinus (Fig. 2).Due to the large size of the tumour, a two-stage procedure was</p><p>advised. The goal of the first procedure was to remove the centraltumour segment. This would allow the two smaller components toascend closer to the surface and enable better visualisation at thesecond stage, thus decreasing the risk of damage to eloquent areas.The first operation revealed that the tumour had extensively in-vaded and destroyed the overlying bone. This was removed untila healthy margin was reached. The central part of the tumour wasa whitish-grey colour, was highly vascular and friable and wastotally removed.Postoperatively, the patient had motor weakness on her left side</p><p>(2/5) that was treated conservatively with corticosteroids andphysical therapy and progressively recovered. Histopathologicalexamination showed neoplastic tissue consisting of a homogenouspopulation of small cells with deeply stained oval nuclei, scantycytoplasm and strongly positive for synaptophysin CD99 (Fig.3). The cells were growing within a fibrillary network and amongthem some larger cells with neuronal morphology were also iden-tified. The gross and microscopic morphology of the tissue and theresults of the immunocytochemical analysis were consistent withthe diagnosis of PNET with glial and cartilaginous differentiation.Due to propensity of PNET to metastasise via the CSF path-</p><p>ways, an MRI of the whole neuraxis with contrast enhancementwas obtained but no other lesion was demonstrated. The secondoperation was performed 4 months later in another hospital andcomplete tumour removal was achieved with no neurologic defi-cits. The patient refused irradiation or chemotherapy. She is cur-</p><p>rently under clinical and radiological follow up and 24 monthsafter the first operation there are no signs of recurrence.</p><p>DISCUSSION</p><p>Bailey and Cushing first reported PNET in 1924. They described aseries of 25 patients with tumours that seemed to arise from the4th ventricle and protrude into the cerebellum. Initially, theynamed this tumour cerebellar spongioblastoma. However, in1925, they extended their series to a total of 29 patients and re-named the tumour cerebellar medulloblastoma. Under this head-ing, low-grade differentiated tumours of the cerebellum werealso included, originating around the 4th ventricle and occurringmainly in children. The term cerebellar medulloblastoma was se-lected due to the assumption that the tumour originated from theprimitive myeloblast, a neuronal stem cell able, in theory, to dif-ferentiate to all neuronal cell types.2</p><p>In 1973, Hart and Earl3 introduced the term primitive neuroec-todermal tumour/PNET to describe embryonal neoplasms arisingoutside the cerebellum but morphologically similar to medullo-blastoma. In 1983, Rorke suggested the inclusion of the termmedulloblastoma within the broader category of PNET4 onthe basis of their histological similarity to other CNS tumoursoriginating from the malignant transformation of primitive neuro-epithelial cells. This classification was accepted by the World</p><p>Fig. 1 T1-weighted coronal MRI showing a large supratentorial lesion</p><p>located on the mid- and parasagittal convexity of both hemispheres.</p><p>Fig. 2 Lateral digital subtraction angiogram showing considerable</p><p>downward displacement of the superior sagittal sinus by tumour (arrows).</p><p>Fig. 3 Microscopy of the tumour, showing a PNET with glial and</p><p>cartilaginous differentiation, consisting of small cells with oval nuclei and</p><p>scanty cytoplasm. The tumour stained strongly positive for CD99.</p><p> 2005 Elsevier Ltd. All rights reserved. Journal of Clinical Neuroscience (2005) 12(4)</p><p>493Adult supratentorial primitive neuroectodermal tumor</p></li><li><p>Health Organization (WHO) in 19855 and in 1993, in the WHOclassification of brain tumours, the term PNET was assignedto both medulloblastoma and other histologically similar CNStumours that did not necessarily originate from the cerebellum(PNET/medulloblastoma if within the cerebellum, supratentorialPNET if outside the cerebellum).6</p><p>The precise relationship of PNET to cerebellar medulloblas-toma, however, remains speculative largely due to the fact thattheir true cellular origin and histogenesis are not yet clarified. Re-cent studies by Gyure et al.7 and Russo et al.8 (1999), revealedconsiderable differences between medulloblastoma and otherPNET, both at the genetic and immunohistochemical level andtheir studies suggested these tumours to be distinct biological enti-ties. The final classification of PNETs thus remains ill defined.With their histogenesis incompletely understood, different groupsof investigators have offered their own interpretations and haveused the term in different ways, seldom defining their pathologiccriteria in a clear and specific manner.The underlying uncertainty over pathologic definitions under-</p><p>mines the validity of the clinical characteristics and comparisonof cases reported as PNET. The classification evolved from theoriginal work of Bailey and Cushing, was elaborated upon byRubinstein9 in 1972 and is based on the hypothesis that the pri-mordial neural tube cells constitute the cellular series of originfor medulloblastoma. Given the variety of the histopathologiccharacteristics of PNET, inherent in this tenet is also the presump-tion that neural tube embryonic cells are capable of differentiatingto all cell types in the nervous system, including neuroglia, neu-rons and ependymal cells. This hypothesis, though popular, re-mains unproven. According to the scheme of Rubinstein9</p><p>(Table 1), six different types of PNETs are recognised. Addition-ally, the retinoblastoma is sometimes incorporated in this schemedue to the primitive morphology of its constituting cells and theirpotential ability to differentiate towards either neuroblasts or pho-toreceptor cells.10</p><p>The uncertainty that prevails regarding the histogenesis andclassification of PNETs has led to equal uncertainty in definingand comparing the various clinical characteristics of these tu-mours within reported series.10 Furthermore, while these tumoursare uncommon even in children, in whom they constitute about 37% of primary brain tumours;11 reports in the literature of suchneoplasms occurring in the supratentorial compartment of adultsare rare.The clinical presentation is generally non-specific and no char-</p><p>acteristic symptom or sign has been described.1 It includes mostlysymptoms and signs of increased intracranial pressure of recentonset as a consequence of rapid tumour growth. Patients usuallycomplain of morning headaches frequently accompanied by vom-iting; the headache is sometimes localised in the occipital area, asa result of a postulated small degree of cerebellar tonsillar herni-ation. Papilledema is frequent. Focal neurological signs appear asa result of local pressure on the brain parenchyma.Radiological characteristics vary considerably. Commonly,</p><p>these are sizeable heterogeneous lesions on CT and MRI, with cys-tic and necrotic regions (the latter implying rapid growth). Focal</p><p>intratumoural calcification is not uncommon, thus CT is importantbecause calcification is helpful in the differential diagnosis frommetastatic brain tumour and high-grade astrocytoma.1 Haemor-rhage into the tumour bed is not infrequent, while in some casesa large degree of peritumoural oedema is also present. DSA usuallyreveals a rich vascular supply and is indicated in all cases of sus-pected PNETs since pre-operative embolisation of feeding vessels,if feasible, may assist operative resection. In our reported case, thepatte...</p></li></ul>