Different incidence of loss of heterozygosity on chromosome 16q between intraductal papilloma and intracystic papillary carcinoma of the breast.

Loss of heterozygosity (LOH) on chromosome 16q was examined in DNA isolated from 11 intraductal papillomas and 12 intracystic papillary adenocarcinomas of the breast. Such LOH was detected in 8 (67%) out of 12 intracystic papillary adenocarcinomas, and in 7 (64%) of 11 of these adenocarcinomas of low grade atypia (Grade 1), whereas it was not detected in 11 intraductal papillomas. Therefore, inactivation of tumor-suppressor genes on chromosome 16q was suggested to be involved in acquisition of malignant phenotype rather than in tumorigenesis in mammary gland epithelial cell. Examination of LOH on 16q should be helpful for differential diagnosis of intracystic papillary tumors.