Since it is known that the tumor suppressor gene PTEN (located on chr10q23) is frequently inactivated in glioblastomas through mechanisms including partial or entire loss of chromosome 10 [21] we reasoned that increased expression of genes on chromosome 10 might be an indication of the intactness of chromosome 10, reflecting the absence of PTEN LOH. The gene discussed is PTEN; the disease is glioblastoma.