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  • Updated 08.25.2018
  • Released 08.22.1995
  • Expires For CME 08.25.2021

Pilocytic astrocytoma in adults

Introduction

Overview

The author reviews the biology, clinical presentation, and treatment options available for adult patients with pilocytic astrocytomas. These uncommon tumors are generally slow growing and benign, with a favorable long-term prognosis compared to the more frequently diagnosed tumors in adults.

Key points

• Pilocytic astrocytoma is classified by the World Health Organization as a grade 1 tumor—low-grade astrocytoma with an indolent course in most cases.

• MRI typically shows a cystic mass with an enhancing mural nodule.

• A small percentage of cases will have a more aggressive course.

• Gross total resection may be curative in many cases.

• Rarely, progressive or recurrent cases may need treatment with radiotherapy and/or chemotherapy.

Historical note and terminology

The seminal descriptions of what are now termed "pilocytic astrocytoma" were made by Ribbert and later by Bailey and Cushing in an early brain tumor classification of theirs, using the name "spongioblastoma" (162; 09; 215). Nosologically, it did not seem appropriate to many investigators to use the term "spongioblastoma," (which implied a primitive neoplasm with malignant growth potential) to describe a tumor that behaved in a benign fashion and carried a relatively good prognosis (213). Penfield adopted the term "piloid astrocytoma" instead of "spongioblastoma" to describe this unique group of tumors that contained elongated, pointed bipolar or multipolar cells (153). Other investigators coined the phrase "astrocytoma of the juvenile type" because of the propensity of these neoplasms to occur in children, adolescents, and young adults (90; 170). Bergstrand described tumors with cells that formed intersecting bundles like "waves of hair" and called them "gliocytoma embryonale" (15). Extensive work by Zulch eventually led to the conclusion that the apparently disparate tumors described by Bailey and Cushing, Penfield, Kagan, and Bergstrand were in fact a single entity (213; 215). The World Health Organization now classifies all "piloid" tumors that have the appropriate characteristics (occurrence in the cerebrum or near the midline, microcystic, or macrocystic regions, presence of Rosenthal fibers and granular bodies, lack of mitoses and nuclear pleomorphism, etc.) as pilocytic astrocytomas (astrocytoma, grade 1), regardless of the age of the patient (214; 215). Although uncommon, an adult form of pilocytic astrocytoma can occur that has a different histological appearance than the more common juvenile pilocytic tumors, and has been recognized as a separate clinical entity since 1959 (172).

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