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Computerixd Medical Imaging and Graphics. Vol. 16. No. 4. pp. 291-295, 1992 Printed in the U.S.A. All rights reserved.

PRIMITIVE NEUROEaODERMAL CT, MRI, AND ANGIOGRAPHIC

TUMOR: FINDINGS

Scott D. Long and Matthew J. Kuhn* Southern

Illinois University

School of Medicine,

Division

of Neuroradiology,

Springfield,

IL 62769

(Received 28 October 1991) Abstract-Primitive neuroectodermal tumors (PNETs) are uncommon CNS neoplasms found usually in the first decade of life. This article presents a proven case of this lesion in a 14-month-old boy located deep in the left

frontal lobe. This lesion was studied by CT, MRI, and cerebral angiography. The radiologic findings of this tumor were assessed and compared with those eases reported in the medical literature. Key Words: Primitive neuroectodermal tumor, PNET, CT, MRI, Cerebral angiography

lobe (Figs. 5, 6). The mass-produced intense homogeneous enhancement with central hypodensity after i.v. administration of non-ionic contrast (Figs. 7, 8). The mass measured 2.5 X 2.0 cm with a sharp margin and produced very minimal midline shift. The differential diagnosis included a glioma or a partially thrombosed AVM. PNET was also a consideration. Subsequently, angiography showed no enhancing lesion or evidence of neovascularity (Figs. 9, 10, 11, 12). The patient underwent a left frontal craniotomy. A soft, friable, intra-axial tumor without any capsule presented deep in the inferior left frontal lobe. Frozen section revealed a malignant appearing neuroectoderma1 tumor. Final pathological diagnosis was that of a PNET, of primary origin within the brain parenchyma.

INTRODUCTION Primitive neuroectodermal tumors (PNETs) are rare tumors of the CNS primarily affecting children and young adults. PNETs are usually supratentorial; a few cases have been reported in the spinal cord. Although PNETs are usually associated with a poor prognosis, limited success has been achieved with combined treatment of surgery, radiation, and chemotherapy. We present a lCmonth-old boy with a proven case of PNET who was studied by CT, MRI, and angiography. CASE REPORT A 14-month-old boy with normal birth history and developmental milestones, presented with vomiting, irritability, and a jerking of the left foot. The patient then developed a partial focal seizure which progressed to a generalized tonic-clonic seizure. On admission to the hospital, the patient was in no acute distress, although pale and lethargic. Head circumference, length, an’d weight were all within the 80th percentile. The patient had no definite neurological findings except for the presence of bilateral Babinski signs. MRI of the head was performed. T l-weighted axial and sagittal images demon.strated a heterogeneous, hypointense mass in the inferior left frontal lobe with no associated edema (Figs. 1: 2). The central portions of the mass was bright on T2-weighted axial and coronal images (Figs. 3, 4). Non-contrast CT scan revealed a hyperdense, noncalcified mass in the inferior left frontal

DISCUSSION In 1973, Hart and Earle (1) defined a group of supratentorial brain tumors with common clinical and pathological findings as PNETs. These tumors are composed of 90 to 95% undifferentiated cells with focal areas of glial or neuronal differentiation. The undifferentiated cells resemble matrix cells of the embryonic neural tube (1). Previously, PNETs have been classified as cerebral neuroblastomas, undifferentiated gliomas, cerebral medulloblastomas, and small cell tumors (2). Histologically, the posterior fossa medulloblastoma resemble PNET with undifferentiated cells and focal areas of glial or neuronal differentiation. However, a separate designation is justified as medulloblastomas are usually found in the cerebellum and are not an uncommon tumor in children (3). The pathologic characteristics of a PNET are quite consistent. Histologically, the tumors are predominantly (90-95s) composed of small undifferentiated

* Correspondence should be addressed to Matthew J. Kuhn, Southern Illinois University, School of Medicine, Division of Neuroradiology, 800 East Carpenter :Street, Springfield, IL 62769. 291

Fig 2

Fig 1

Figs. 1 and 2. MR axial and sagittal Tl-weighted images demonstrates inferior left frontal lobe.

Fig 3

Figs. 3 and 4. MR axial and coronal T2-weighted

a heterogeneous,

hypointense

mass in the

Fig 4

images show this same mass with a central bright signal abnormality. 292

PNETs

and CT, MRI, and angiography ??S. D. LONG and M. J. KUHN

Fig 5

Figs. 5 and 6. Non-contrast

293

Fig 6

CT showing a hyperdense mass in the inferior left frontal lobe. No appreciable edema or mass effect noted.

cells with a high nuclear-cytoplasmic ratio. There may be focal areas of either glial or neuronal differentiation. Malignant parameters include hypercellularity, pleomorphism, numerous mitotic figures, vascular endothelial hyperplasia, and areas of necrosis (1, 3, 4). Grossly PNETs are soft, lobulated masses with frequent

Fig 7

sharp margins. Areas of necrosis, calcification, hemorrhage, and cyst formation are commonly present ( 1, 3,4). PNETs most commonly occur in the first decade of life (5). One study of 3 1 patients had more than 50% which presented by age 3, and 70% by age 6 (2). These

Fig 8

Figs. 7 and 8. Contrast CT displays intense enhancement of the mass with a hypodense central region possibly secondary to necrosis. The mass is sharply demarcated and measures 2.5 X 2.0 cm.

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Computerized Medical Imaging and Graphics

July-August 1992, Volume 16, Number 4

Fig 9

Fig 10

Fig 11

Fig 12

Figs. 9, 10, 11, and 12. Cerebral angiography (AP and lateral) shows no abnormal tumor vessels or blush. No early draining

veins are demonstrated.

patients presented with symptoms and signs of increased cranial pressure including headache, irritability, vomiting, and papilledema. Hemiparesis and focal seizures are common presentation (1, 2, 4, 6). However, several patients had very little symptoms despite a large tumor bulk (4, 7). As with other CNS lesions, many of the neurological signs correlated with the location

of the tumor. PNETs characteristically are supratentorial in position with the frontal lobe as the most common location, ranging from 20 to 39% of cases ( 1, 2-4, 6). The tumor may arise as a primary lesion in the spinal cord in rare cases (4). PNETs often seed in the intracerebral or spinal subarachnoid space (2, 6, 7). Extracerebral metastasis to the lungs, perihilar

PNETs and CT, MRI, and angiography

lymph nodes, pericardiu:m, diaphragm, liver, and kidney has been reported (4, 8). The PNET is a rapidly growing malignant tumor with a poor prognosis. The average survival period is 8 to 24 months (4). Aggressive treatment consisting of surgical decompression of the tumor followed by radiotherapy and chemotherapy may improve survival rates. Irradiation of the entire neuraxis is recommended due to the tendency of F’NETs to have spinal metastases (4). Unfortunately, them are no specific radiologic features which readily permit preoperative diagnosis from commoner tumors. Skull films have demonstrated split sutures, localized thinning of the vault, and erosion of the inner table over the tumor (3, 5). CT scans generally show atlarge isodense supratentorial mass. Non-contrast CT demonstrates an isodense to hyperdense mass with little or no associated edema (2, 6). One study (2) noted calcification in the tumor in 7 1% of the cases. PNETs often enhance with contrast administration showing a dense, heterogeneous pattern (2). The enhanced tumor appears sharply demarcated from surrounding brain tissue with either a solid or ring pattern (6). Hypodense areas of cysts and necrosis are common within the tumor mass (2, 5,6). The ring enhancement of some PNETs with cystic and necrotic areas may suggest abscess formation. The MR appearance of a primitive neuroectodermal tumor appears as a mild to moderate hypointense mass on Tlweighted images and as heterogeneous areas of increased signal intensity on TZweighted images. PNETs enhance with intravenous gadolineum. Spontaneous subacute and chronic intratumoral hemorrhages display hyperdense T 1 signal (7). Unlike the CT and MRI, the angiographic appearances of PNETs have been variable. Most investigators have found the angiographic appearance to range from considerable vascularity to complete avascularity (2, 5, 6). A lCmonth-old infant with a classical primitive neuroectodermal tumor is presented with characteristic CT, MRI, and angiographic findings which were described by other investiga.tors. Although a rare neoplasm, the PNET should be a consideration as differ-

S. D. LONG and M. J. KUHN

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ential diagnosis in any child presenting with a hyperdense, intra-axial, supratentorial mass in CT scanning. SUMMARY Primitive neuroectodermal tumors (PNETs) are uncommon CNS neoplasms found usually in the first decade of life. We present a proven case of this lesion which was studied by CT, MRI, and cerebral angiography. The radiographic findings of this tumor were compared with those cases previously reported in the medical literature. Primitive neuroectodermal tumors should be considered in the differential diagnosis of pediatric brain neoplasms. REFERENCES 1. Hart, M.N.; Earle, K.M. Primitive neuroectodermal tumors of the brain in children. Cancer 32:890-896; 1973. 2. Altman, N.; Fitz, C.R.; Chuang, S.; Harwood-Nash, D.; Cotter, C.; Armstrong, D. Radiologic characteristics of primitive neuroectodermal tumors in children. AJNR 6: 15- 18; 1985. 3. Kosnik, E.J.; Boesel, C.P.; Bay, J.; Sayers, M.P. Primitive neuroectodermal tumors of the central nervous system in children. J. Neurosurg. 48:741-746; 1978. 4. Cohen, M.E.; Duffner, P.K. Brain Tumors in Children: Principles of Diagnosis and Treatment. New York Raven Press, 1984:273279. 5. Kingsley, D.P.E.; Harwood-Nash, D.C.F. Radiologic features of the neuroectodermal tumours of childhood. Neuroradiology 26: 463-467; 1984. 6. Ganti, S.R.; Silver, A.J.; Diefenbach, P.; Hilal, S.K.; Mawad, M.E.; Sane, P. Computed tomography of primitive neuroectodermal tumors. AJNR. 4:19-21; 1983. 7. Cohen, M.D.; Edwards, M.K. Magnetic Resonance Imaging of Children. Philadelphia, PA: B.C. Decker, Inc.; 1990:180-l 8 1, 8. Hinshaw, D.B.; Ashwal, S.; Thompson, J.R.; Hasso, A.N. Neuroradiology of primitive neuroectodermal tumors. Neuroradiology 2587-92; 1983.

About the Author-Sco-rr D. LONG is a fourth-year medical student at Southern Illinois University in Springfield, IL. He received the B.S. degree in Biology from the University of Illinois Urbana-Champaign in 1988. He has been involved with clinical research the past two years and has assisted in the completion of several manuscripts. He plans to pursue a postgraduate position in diagnostic radiology. About the Author-MATTHEW J. KUHN, M.D., is the chief of neuroradiology and Associate Professor of Radiology, Neurology, and Neurosurgery at the Southern Illinois University School of Medicine in Springfield, IL.

Primitive neuroectodermal tumor: CT, MRI, and angiographic findings.

Primitive neuroectodermal tumors (PNETs) are uncommon CNS neoplasms found usually in the first decade of life. This article presents a proven case of ...
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