(C-A)n microsatellite repeat D7S522 is the most commonly deleted region in human primary breast cancer.

Loss of heterozygosity in human chromosome 7q was studied to determine the location of a putative tumor suppressor gene. Twenty-six of 31 cases studied presented loss of heterozygosity at one or more loci on chromosome 7q. Eighty-three percent loss of heterozygosity (in 11 informative cases) was detected by using the (C-A)n microsatellite repeat marker D7S522 at 7q31.1-7q31.2. These results suggest that a tumor suppressor gene relevant to the development of breast cancer is present in the 7q31.1-7q31.2 region, confirming our previous evidence for a tumor suppressor gene in this chromosome and frequent deletions of the long arm in human primary breast cancers.