Pediatric Intracranial Germinomas

Abstract

Epidemiology Intracranial germ cell tumors (IGCT) account for 3–5% of pediatric central nervous system malignancies in the United States, though the incidence can be as high as 10–11% in some Asian countries [1]. Demographics Germinomas are most commonly seen in adolescents aged 10–12 years with 90% occurring before age 20 years. A male predominance is noted for IGCTs, in particular for tumors of pineal gland origin [1, 2]. Histological subtypes IGCTs are broadly classified by the World Health Organization (WHO) into pure germinomas and non-germinomatous germ cell tumors (NGGCT). The majority, two-thirds, are pure germinomas with the remaining one-third NGGCTs [2]. NGGCTs are subclassified into [1] embryonal, [2] yolk sac or endodermal sinus, [3] choriocarcinoma, [4] teratoma (immature, mature, and malignant transformed), and [5] mixed germ cell tumor (farraginous components of NGGCT and pure germinoma) [2]. Anatomy and patterns of spread There is an intimate association with midline proximal third ventricular structures, specifically the pineal and suprasellar (e.g., infundibulum and pituitary stalk) regions, which make up nearly two-thirds and one-third of observed IGCTs, respectively. Less common locations include the basal ganglia and thalamus [1, 3]. Up to 10% of patients present with bifocal disease, more commonly seen in pure germinomas, which is believed to represent multifocal occurrence of tumors and not metastatic disease. These patients are treated as though they have localized disease [3–5]. CSF dissemination occurs in 10–20% of patients [1]. Prognosis IGCTs treated with standard therapy demonstrate exceptional long-term disease-free survival of >90% and 70–80% for pure germinomas and NGGCTs, respectively [1]. The Japanese Pediatric Brain Tumor Study Group Classification categorizes patients into three prognostic groups based on histology for patients that have resection of tumor up front: [1] “good” with a 10-year survival >90%, [2] “intermediate” with a 3-year survival of ~70%, and [3] “poor” with a 3-year survival 10–30% [6]. In the United States and Europe, it is uncommon to perform surgical resection up front for full pathologic evaluation of the tumor.