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  • Updated 11.03.2020
  • Released 08.29.1995
  • Expires For CME 11.03.2023

CNS germinoma

Introduction

Overview

Intracranial germinomas are relatively rare tumors that most often occur in childhood and adolescence. They typically arise in the pineal and suprasellar regions, and frequently present with signs of increased intracranial pressure (ICP), endocrine abnormalities, and visual changes. In this article, the author expands our view of the molecular pathogenesis of this neoplasm, highlights novel markers used in the diagnosis of this tumor, and reviews modifications in treatment strategies.

Key points

• Chemotherapy alone is toxic and inferior to modest chemoradiation therapy regimens.

• Treatment considerations are different for adults than for skeletally and neurologically immature children (generally younger than 12 years old).

• For localized disease, the recommended radiotherapy volume is whole ventricular field plus boost to the primary tumor site regardless of whether or not chemotherapy is given.

• For metastatic disease, the recommended radiotherapy volume is craniospinal plus boost to the primary tumor site regardless of whether or not chemotherapy is given.

• Chemoradiation therapy may allow radiation dose reduction but not volume reduction.

• Long-term data are still needed to determine if chemoradiation therapy provides meaningful reductions in cognitive and endocrine toxicity in adults compared to radiation therapy alone.

Historical note and terminology

Tumors arising in the posterior third ventricular and suprasellar regions represent a variety of cell types, including those derived from ectopic primordial germ cells, and those derived from cellular elements intrinsic to the CNS (62). In addition, pineal and suprasellar metastases from systemic malignancies can occur. Tumors derived from primordial germ cells are designated primary CNS germ cell tumors (GCTs). Germ cell tumors can be divided into 2 major groups: germinomas and “nongerminomatous” germ cell tumors (NGGCTs). Nongerminomatous germ cell tumors include: embryonal carcinoma, yolk sac (endodermal sinus) tumor, choriocarcinoma, mature and immature teratoma, teratoma with malignant transformation, and mixed germ cell tumors. Histologic, electron microscopic, immunohistochemical, and molecular biological studies have confirmed the similarity of intracranial germinoma and nongerminomatous germ cell tumors to their extraneural analogues (15).

Germinomas are the most common of the intracranial germ cell tumors, accounting for 50% to 70% of germ cell tumors (54; 117; 130). Germ cell tumors, both neural and extraneural have a predilection for midline structures, occurring primarily in the pineal and suprasellar regions in the CNS and peripherally in the sacrococcygeal region, retroperitoneum, and mediastinum. Uncommonly, germinomas may occur in the basal ganglia (5% to 10% of cases), thalamus, fourth and lateral ventricles, cerebellum, cerebellopontine angle, and spinal canal (54; 106; 44; 100). Although extremely rare, germinoma in the brainstem has also been described (87). Multifocal tumors involving both the pineal gland and neurohypophysis, and sometimes diffusely involving the third ventricle and adjacent structures, have been reported in 2% to 8% of cases. Case series using neuroimaging techniques, have recorded bifocal (pineal and suprasellar) or multifocal involvement in about 18% of cases (04; 11; 76; 115; 12; 16). Metastatic spread can occur through the subependymal space and cerebral spinal fluid (CSF), but can also spend along the ventricular surface (09). The incidence of CSF dissemination at presentation is difficult to determine because of various methods of assessment, but in the modern era about 14% of patients were diagnosed with disseminated disease by MRI scanning or CSF cytology (66; 25; 121; 11; 46; 117; 39; 07; 115; 12; 16; 18); the true incidence may be somewhat higher.

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