Graziella Filippini*
Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
*Correspondence to: Graziella Filippini, Istituto Nazionale Neurologico ‘C. Besta’, Via Celoria 11, 20133 Milan, Italy.
E-mail address: gfilippini@istituto-besta.it
Abstract
The descriptive epidemiology of primary central nervous system (CNS) tumors is based on population-based cancer registries that include tumors of the brain, cranial nerves, cerebral meninges, spinal cord, and spinal meninges. Malignant CNS tumors in adults account for 1.7% of new cancers and 2.1% of cancer deaths. In Europe, Australia/New Zealand, and North America there are 7.5–14 new cases per 100 000 population per year in males, and 4–11 new cases in females. Incidence rates of benign and borderline CNS tumors are available from the Surveillance, Epidemiology, and End Results (SEER) Program for the time period 1975–2004: incidence was 8.1 new cases per 100 000 population per year in males, and 12.1 in females. Incidence and mortality significantly increased in white males and females from 1975–1991; subsequently, the incidence remained steady, and mortality decreased significantly from 1992–2004. In population-based studies less than 5% of glioma risk is hereditary. Well-identified genetic syndromes that include primary brain tumors (PBTs) are most often autosomal dominant, and have variable penetrance. The most common syndrome is neurofibromatosis type 1. Ionizing radiation has a proven etiological role in experimental studies in monkeys and primates and, as a late complication of therapeutic X-irradiation, in humans. Extensive epidemiological research conducted during the past 20 years on occupational electromagnetic field exposure did not indicate strong or consistent associations with adult PBTs. The WHO/IARC has classified RF electromagnetic fields as possibly carcinogenic to humans (Group 2B) based on an increased risk for glioma associated with wireless phone use. Additional research needs to be conducted into the long-term use of mobile phones.
Introduction
The descriptive epidemiology of the central nervous system (CNS) tumors is based on population-based cancer registries that include tumors of the brain, cranial nerves, cerebral meninges, spinal cord, and spinal meninges.
The anatomical classification of tumors used in cancer registries has followed the evolution of the World Health Organization (WHO) International Classification of Diseases (ICD), now in its 10th revision (ICD-10; WHO, 1992), and the coding scheme for oncology, the International Classification of Diseases for Oncology (ICD-O, 3rd edition; WHO, 2000). CNS tumors are represented by the ICD-O topographical codes: C70.0–9, meninges; C71.0–9, brain; C72.0–9, spinal cord, cranial nerves, and other parts of the CNS; C75.1–C75.3, the pituitary and pineal gland. Histological subgroups are defined by the morphological terms of the ICD-O and behavior is coded /0 for benign tumors, /1 for low or uncertain malignant potential or borderline malignancy, /2 for in and /3 for malignant tumors (Table 1.1). In population-based cancer registries the topographical codes C70–72 are grouped together in the ‘brain, nervous system’ group, and only tumors of malignant behavior (code /3) are included and combined.
Table 1.1 World Health Organization classification of primary central nervous system tumors (ICD-O, 2000)
| Histological type | ICD-O morphology code/behavior code* |
| Tumors of neuroepithelial tissue Astrocytic tumors | |
| Diffuse astrocytoma | 9400/3 |
| Fibrillary astrocytoma | 9420/3 |
| Protoplasmic astrocytoma | 9410/3 |
| Gemistocytic astrocytoma | 9411/3 |
| Anaplastic astrocytoma | 9401/3 |
| Giant cell glioblastoma | 9441/3 |
| Pilocytic astrocytoma | 9421/1 |
| Pleomorphic xanthoastrocytoma | 9424/3 |
| Subependymal giant cell astrocytoma | 9384/1 |
| Anaplastic oligodendroglioma | 9451/3 |
| Anaplastic ependymoma | 9392/3 |
| Myxopapillary ependymoma | 9394/1 |
| Choroid plexus papilloma | 9390/0 |
| Choroid plexus carcinoma | 9390/3 |
| Glial tumors of uncertain origin | |
| Gliomatosis cerebri | 9381/3 |
| Neuronal and mixed neuronal–glial tumors | |
| Pineal parenchymal tumors | |
| Medulloepithelioma | 9501/3 |
| Supratentorial primitive neuroectodermal tumor (PNET) | 9473/3 |
| Meningotheliomatous meningioma | 9531 |
| Psammomatous meningioma | 9533 |
| Hemangioblastic meningioma | 9535 |
| Hemangiopericytic meningioma | 9536 |
| Transitional (mixed) meningioma | 9537 |
NOS, not otherwise specified.
* Morphology code of the International Classification of Diseases for Oncology (ICD-O). Behavior is coded /0 for benign tumors, /1 for low or uncertain malignant potential or borderline malignancy, (/2 for ), and /3 for malignant tumors.
Adapted and reprinted with permission from WHO (2000). ©WHO.
Since the publication of the first edition of the ICD-O (WHO, 1976), cancer registries have adapted their operative systems to the standard classification and coding rules, but the definition, classification, and grouping of cancers have varied considerably among registries. Therefore, caution is required when comparing incidence rates over time, because the observed differences may be the result of changes in the methodology used by the different registries.
