RATIONALE: Analyzing the number and structure of genes found in a child's cancer cells may help doctors improve methods of diagnosing and treating children with brain tumors.

PURPOSE: This clinical trial is studying the number and structure of genes in cancer cells of children with brain tumors.

OBJECTIVES:

• Determine the chromosomal gains and losses by DNA ploidy analysis and comparative genomic hybridization in patients with primitive neuroectodermal tumors or medulloblastomas.
• Determine the frequency of specific chromosomal abnormalities, including deletions of chromosomal regions 6, 17, and 22, in these patients.
• Perform a statistical analysis to determine possible associations of chromosomal abnormalities and DNA ploidy with patient age, tumor histology, tumor location, extent of disease, and event-free survival.

OUTLINE: DNA ploidy analysis will be performed to determine the overall level of aneuploidy. The results are compared to the comparative genomic hybridization (CGH) analysis, which is used to demonstrate tumor-specific losses or gains, including amplification, of specific chromosomal regions. Tumors are also screened for specific abnormalities by fluorescent in situ hybridization (FISH), which detects chromosomal rearrangements, including balanced translocations, deletions, amplifications, etc. PCR-based microsatellite polymorphism analysis may also be performed.

Primitive neuroectodermal tumors (PNETs) are screened by FISH with a distal 17p13.3 cosmid and a 17q25 cosmid to identify tumors with a 17p deletion. Atypical teratoid/rhabdoid tumors and PNETs without a 17p deletion are screened by FISH with a series of cosmids from 22q11.2. PNETs are also screened by interphase FISH with cosmids from chromosome 6 to identify tumors with deletions.

Patients do not receive the results of the genetic testing and the results do not influence the type or duration of treatment.

PROJECTED ACCRUAL: This study will accrue 360 specimens.

• Genetic: DNA ploidy analysis
• Genetic: comparative genomic hybridization
• Genetic: cytogenetic analysis
• Genetic: fluorescence in situ hybridization

DISEASE CHARACTERISTICS:

• Histologically confirmed primary CNS malignancy consistent with primitive neuroectodermal tumor, medulloblastoma, or atypical teratoid/rhabdoid tumor
• Must be entered on CCG-9921, CCG-9931, CCG-A9961, CCG-99703 or other front-line studies developed from CCG-90024 or CCG-90025
• Retrospective specimens also obtained from CCG-921, CCG-923, CCG-9892, CCG-9921, and CCG-9931

PATIENT CHARACTERISTICS:

Age:

• Under 21

Performance status:

• See Disease Characteristics

Life expectancy:

• See Disease Characteristics

Hematopoietic:

• See Disease Characteristics

Hepatic:

• See Disease Characteristics

Renal:

• See Disease Characteristics

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• Not specified

Endocrine therapy

• Not specified

Radiotherapy

• No prior radiotherapy

Surgery

• Not specified