In malignant gliomas, the characteristically heterogeneous features and frequent 
diffuse spread within the brain have raised the question of whether malignant 
gliomas arise monoclonally from a single precursor cell or polyclonally from 
multiple transformed cells forming confluent clones. Although monoclonality has 
been shown in surgically resected tissues, these may not include the full 
spectrum of patterns seen on autopsy material. Little is known about the 
clonality of low-grade gliomas from which malignant gliomas may sometimes arise. 
We sought to investigate the clonality of low-grade and malignant gliomas by 
using and comparing surgical and autopsy material with a Polymerase chain 
reaction (PCR)-based assay for nonrandom X chromosome inactivation. For that, 
purpose, archival surgical and autopsy material from 15 female patients (group 
A) (age 4 to 73 years; median, 45) with malignant gliomas (12 glioblastomas, one 
gliosarcoma, one anaplastic oligoastrocytoma, one gliomatosis cerebri), surgical 
material only from 21 female patients (group S) (age 6 to 78 years; median, 60) 
with low-grade and malignant gliomas (four low-grade astrocytomas, three 
oligoastrocytomas, two anaplastic astrocytomas, one gemistocytic astrocytoma, 
four oligodendrogliomas, seven glioblastomas) were analyzed. In group A, 
representative areas (mean = 5/patient; median = 7) were microdissected from 
tissue sections and assayed by PCR amplification of a highly polymorphic 
microsatellite marker locus of the human androgen receptor gene (HUMARA) in the 
presence of alpha32P with and without predigestion with a methylation-sensitive 
restriction enzyme (HhaI). Products were resolved by denaturing gel 
electrophoresis and autoradiographed. In group S, selected tumor areas were used 
for the assay. Each patient's normal brain tissue was used for control. The band 
intensity of alleles were measured by densitometric scanning. In group A, 13 of 
15 cases were informative (heterozygous). The same pattern of nonrandom X 
chromosome inactivation was present in all areas of solid dense and moderate 
tumor infiltration in eight including all components of the gliosarcoma. Two of 
eight also showed focal loss of heterozygosity (LOH). One of 13 presented global 
LOH. Two of 13 showed microsatellite instability, one of which in a patient with 
Turcot syndrome, the other in gliomatosis cerebri. Opposite skewing patterns 
were seen in distant areas of gliomatosis cerebri consistent with oligoclonal 
derivation. Clonality remained indeterminate in one glioblastoma and in the 
anaplastic oligoastrocytoma because of skewed lyonization in the normal control. 
In group S, 19 of 21 cases were informative. Fifteen of 19 were monoclonal (four 
low-grade astrocytomas, one anaplastic astrocytoma, one gemistocytic 
astrocytoma, two oligodendrogliomas, one oligoastrocytoma, six glioblastomas). 
Four of 19 were indeterminate. We conclude that (1) Low-grade and malignant 
gliomas are usually monoclonal tumors, and extensively infiltrating tumors must 
result from migration of tumor cells (2) Gliomatosis cerebri may initiate as an 
oligoclonal process or result from collision gliomas (3) Biphasic gliomas likely 
arise from a single precursor cell. (4) LOH at the HUMARA locus is probably 
related to partial or complete deletion of an X-chromosome, which occurs in 
malignant gliomas during clonal evolution.