Radiographs from patient 6 showing homozygous deletion ofPTEN gene.

LOH was found at D10S215 and D10S541, with a 50% to 70% reduction in signal intensity in 1 allele compared with the normal control. The reduction in signal intensity was not 100% because of the presence of normal DNA contaminating the tumor sample. There was retention of heterozygosity at the PTEN intragenic marker D10S2491. This presumably occurred because of loss of both PTEN alleles in the tumor DNA (homozygous deletion) so that only the contaminating normal DNA was amplified to produce 2 alleles with low signal intensity.