eMedicine Specialties > Radiology > Brain/Spine

Juvenile Pilocytic Astrocytoma

Author: Simon Lo, MBBS, Assistant Professor, Department of Radiation Oncology, Indiana University School of Medicine
Coauthor(s): Karl K Kish, MD, Chief, Section of Neuroradiology, Department of Radiology, Harper University Hospital; Eric L Chang, MD, Assistant Professor, Department of Radiation Oncology, University of Texas MD Anderson Cancer Center; Kenneth J Levin, MD, Assistant Professor, Karmanos Cancer Institute, Medical Advisor, Radiation Therapy Technology School, Department of Radiation Oncology, Wayne State University School of Medicine; Clinical Assistant Professor, Medical Laboratory Science, Oakland University School of Health Sciences; Medical Director, Department of Radiation Oncology, North Oakland lMedical Centers and Henry Ford Medical Center; Sameer R Keole, MD, Staff Physician, Department of Radiation Oncology, Gershenson Radiation Oncology Center, Karmanos Cancer Institute, Harper Hospital, Wayne State University School of Medicine; Andrew E Sloan, MD, Associate Professor of Neurosurgery and Radiation Oncology, Case Western Reserve University Medical School; James Fontanesi, MD, Chairman, Department of Radiation Oncology, Cedars-Sinai Medical Center
Contributor Information and Disclosures

Updated: Sep 10, 2008

Introduction

Background

Juvenile pilocytic astrocytomas occur more often in children and young adults. They are the most common astrocytic tumors in children, accounting for 80-85% of cerebellar astrocytomas and 60% of optic gliomas.

Juvenile pilocytic astrocytomas usually arise in the cerebellum, brainstem, hypothalamic region, or optic pathways, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord. The most common site of occurrence of juvenile pilocytic astrocytoma is the cerebellum.¹

These tumors are usually discrete, indolent lesions associated with cyst formation. The cysts may be unilocular or multilocular, with an associated tumor nodule.

The most common presenting symptoms are associated with increased intracranial pressure resulting from mass effect or hydrocephalus. Symptoms may include headache, nausea, vomiting, irritability, ataxia, and visual complaints, depending on the site of occurrence.^{1,2,3,4,5,6,7,8}

Pathophysiology

The etiologic factors of juvenile pilocytic astrocytomas are unknown. Transformation to a malignant high-grade tumor is rare.

Juvenile pilocytic astrocytoma is associated with neurofibromatosis type 1 (NF1), an autosomal-dominant disorder characterized by the development of benign tumors, as well as some malignant tumors. Optic gliomas, 60% of which are pilocytic astrocytomas, are common tumors in patients with this disorder. Patients with optic pilocytic astrocytomas associated with NF1 usually have better outcomes than other patients with juvenile pilocytic astrocytomas because optic pilocytic astrocytomas are more likely to be confined to the optic nerve. Bilateral optic gliomas are more common in patients with NF1.

Macroscopically, an astrocytoma is a well-circumscribed mass that commonly has a large cyst and a focal mural nodule. The tumor may also be solid, with or without cystic degeneration. Microscopically, juvenile pilocytic astrocytoma demonstrates well-differentiated pilocytes with hairlike glial processes associated with microcysts that contain mucopolysaccharide material. The pilocytes are mixed with Rosenthal fibers , eosinophilic rod-shaped bodies, and granular eosinophilic bodies, which are commonly found in indolent neoplasms. Capillary formation is usually present.

Juvenile pilocytic astrocytomas are not graded histopathologically. The 4 morphologic criteria of the Daumas-Duport system — nuclear atypia, mitoses, endothelial proliferation, and necrosis — may sometimes be found in pilocytic astrocytomas, but they have no known prognostic significance.

Frequency

United States

Tumors of the optic pathway account for 3.6-6% of pediatric brain tumors, 60% of which are juvenile pilocytic astrocytomas. Astrocytomas account for 50% of pediatric primary central nervous system tumors. About 80-85% of cerebellar astrocytomas are juvenile pilocytic astrocytomas.

Mortality/Morbidity

Patients with juvenile pilocytic astrocytoma have a better prognosis than patients with most other types of astrocytomas. If gross total resection is possible, the 10-year survival rate is as high as 90%. After subtotal resection or biopsy, the 10-year survival rate is as high as 45%. Morbidity is related to the location of the tumor and to the associated complications of tumor resection.

Sex

The incidence of juvenile pilocytic astrocytomas is the same for males and females.

Age

The peak incidence is in patients 5-14 years of age. Age affects the clinical course of optic nerve gliomas. Of children younger than 5 years, the mortality rate is comparable to that of patients aged 5-20 years.^6,9,8

Anatomy

Juvenile pilocytic astrocytomas usually arise in the cerebellum, brainstem, hypothalamic region, or optic pathways, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and spinal cord.

Presentation

The presenting signs and symptoms of juvenile pilocytic astrocytoma depend on the location of the tumor. The most common symptoms are the result of increased intracranial pressure, caused by a mass effect, or hydrocephalus. Such symptoms include nausea, vomiting, headache, ataxia, and visual effects.

Astrocytic tumors are categorized into pilocytic and ordinary subtypes. The ordinary subtypes include fibrillary, protoplasmic, and gemistocytic tumors. Ordinary astrocytomas are associated with a worse overall prognosis because of their more aggressive behavior and their potential to undergo malignant transformation.

The classic juvenile pilocytic astrocytoma arises in a cerebellar hemisphere; it is easily seen on CT scans and MRIs as a well-circumscribed lesion with an associated macrocyst. The nodular portion of the lesion usually demonstrates homogeneous contrast enhancement. Calcification is present in 10% of juvenile pilocytic astrocytomas. Other low-grade gliomas are typically hypoattenuating or hypointense, poorly defined, nonenhancing lesions on CT scans and MRIs.

Preferred Examination

The preferred examination is MRI (see Images 1-5).^10,11,12,13

Pilocytic astrocytomas are typically treated with surgery; MRIs are useful in outlining the contrast-enhancing tumor. The tumor should be completely resected whenever possible. Cyst wall enhancement may be seen on MRIs; when such enhancement is present, resection of the entire cyst is indicated.^{14,15,16,17,18}

Limitations of Techniques

Use of radiologic findings alone to identify low-grade gliomas results in an incorrect diagnosis in as many as 50% of cases.

Differential Diagnoses

Brain, Metastases
Medulloblastoma
Oligodendroglioma

Other Problems to Be Considered

Supratentorial juvenile pilocytic astrocytoma

Grade 2 astrocytoma
Oligodendroglioma
High-grade glioma
Ependymoma
Brain metastasis

Optic nerve and optic chiasm hypothalamic gliomas

Craniopharyngioma
Meningioma
Hamartoma
Germinoma
Histiocytosis
Sarcoidosis

Posterior fossa juvenile pilocytic astrocytoma

Grade 2 common astrocytoma
Oligodendroglioma
High-grade glioma
Ependymoma
Medulloblastoma
Brain metastasis

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