Update on MRI in pediatric intracranial germ cell tumors—The clinical and radiological features

The fifth edition of the WHO Classification of Tumors of the Central Nervous System (CNS), published in 2021, is the sixth version of the international standard for the classification of brain and spinal cord tumors. Building on the 2016 updated fourth edition and the work of the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy, the 2021 fifth edition introduces major changes that advance the role of molecular diagnostics in CNS tumor classification. At the same time, it remains wedded to other established approaches to tumor diagnosis such as histology and immunohistochemistry. In doing so, the fifth edition establishes some different approaches to both CNS tumor nomenclature and grading and it emphasizes the importance of integrated diagnoses and layered reports. New tumor types and subtypes are introduced, some based on novel diagnostic technologies such as DNA methylome profiling. The present review summarizes the major general changes in the 2021 fifth edition classification and the specific changes in each taxonomic category. It is hoped that this summary provides an overview to facilitate more in-depth exploration of the entire fifth edition of the WHO Classification of Tumors of the Central Nervous System.

The Central Brain Tumor Registry of the United States (CBTRUS), in collaboration with the Centers for Disease Control and Prevention (CDC) and National Cancer Institute (NCI), is the largest population-based cancer registry focused exclusively on primary brain and other central nervous system (CNS) tumors in the United States (US) and represents the entire US population. This report contains the most up-to-date population-based data on primary brain tumors available and supersedes all previous reports in terms of completeness and accuracy and is the first CBTRUS Report to provide the distribution of molecular markers for selected brain and CNS tumor histologies. All rates are age-adjusted using the 2000 US standard population and presented per 100,000 population. The average annual age-adjusted incidence rate (AAAIR) of all malignant and non-malignant brain and other CNS tumors was 24.25 (Malignant AAAIR=7.06, Non-malignant AAAIR=17.18). This overall rate was higher in females compared to males (26.95 versus 21.35) and non-Hispanics compared to Hispanics (24.68 versus 22.12). The most commonly occurring malignant brain and other CNS tumor was glioblastoma (14.3% of all tumors and 49.1% of malignant tumors), and the most common non-malignant tumor was meningioma (39.0% of all tumors and 54.5% of non-malignant tumors). Glioblastoma was more common in males, and meningioma was more common in females. In children and adolescents (age 0–19 years), the incidence rate of all primary brain and other CNS tumors was 6.21. An estimated 88,190 new cases of malignant and non-malignant brain and other CNS tumors are expected to be diagnosed in the US population in 2021 (25,690 malignant and 62,500 non-malignant). There were 83,029 deaths attributed to malignant brain and other CNS tumors between 2014 and 2018. This represents an average annual mortality rate of 4.43 per 100,000 and an average of 16,606 deaths per year. The five-year relative survival rate following diagnosis of a malignant brain and other CNS tumor was 35.6%, for a non-malignant brain and other CNS tumors the five-year relative survival rate was 91.8%.

The present contribution reports childhood cancer incidence and survival rates as well as time trends and geographical variation. The report is based on the databases of population-based cancer registries which joined forces in cooperative projects such as Automated Childhood Cancer Information System (ACCIS) and EUROCARE. According to these data, which refer to the International Classification of Childhood Cancer, leukemias, at 34%, brain tumors, at 23%, and lymphomas, at 12%, represent the largest diagnostic groups among the under 15-year-olds. The most frequent single diagnoses are: acute lymphoblastic leukemia, astrocytoma, neuroblastoma, non-Hodgkin lymphoma, and nephroblastoma. There is considerable variation between countries. Incidence rates range from 130 (British Isles) to 160 cases (Scandinavian countries) per million children. Incidence rates have shown an increase over time since the mid of the last century. In Europe, the yearly increase averages 1.1% for the 1978-1997 period and ranges from 0.6% for the leukemias to 1.8% for soft-tissue sarcomas. The probability of survival has risen considerably over the past decades, with the EUROCARE data showing an improvement of the relative risk of death by 8% when comparing the 2000-2002 time span to the 1995-1999 period. Regarding the years 1995-2002, the data show an overall 5-year survival probability of 81% for Europe and similar values for the USA. The data presented here describe the cancer situation with a specific, European focus. They are drawn from population-based cancer registries that ensure excellent data quality, and as a consequence represent the most valid European population-based data existing at present. It is also apparent that not all countries have data available from nationwide childhood cancer registries, a situation which warrants further improvement. 2010 Elsevier Ltd. All rights reserved.