Background: It has been suggested that cerebellar medulloblastoma (M) and primitive neuroectodermal tumors (PNET) arising elsewhere in the nervous system, represent a single entity (M/PNET), although this concept is controversial. Cancer registries permit population-based description of cases reported as medulloblastoma, those reported as PNET and description of the aggregate, M/PNET.

Procedure: We reviewed the 768 cases of M/PNET (633 diagnosed medulloblastoma and 135 diagnosed PNET) among persons under 20 years of age in the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) database.

Results: The incidence of M/PNET rose 23%, from 4 per 10(6) person-years in 1973-77 to 4.9 per 10(6) person-years in 1993-98. Cases reported as PNET were more likely than those reported as medulloblastoma to be supratentorial (30.4% vs. 1.9%, P < 0.001) and to be female (42.2% vs. 35.4%, P = 0.13). The difference in 5-year survival between the 600 children with infratentorial medulloblastoma vs. the 49 children with infratentorial PNET was not statistically significant (55% vs. 43%). Regardless of reporting diagnosis, survival was poorer among children age 0-3 years and those with supratentorial tumors. Children diagnosed in the more recent period from 1985-1998 had a longer median survival than children diagnosed in 1973-84 (4.9 years vs. 10 years, P < 0.05). Rates were 42% higher among Whites compared to Blacks (4.5/10(6) person-years vs. 3.1/10(6) person-years, P < 0.01).

Conclusions: We found M/PNET is increasing in incidence and more frequent among Whites. Given that medulloblastoma and PNET are histologically identical and have similar epidemiologic profiles, future studies should provide analyses that combine these entities.