Clonality analysis of intraductal proliferative lesions using the human androgen receptor assay

Recently, it is accepted that invasive breast carcinoma is of monoclonal origin. Ductal intraepithelial neoplasia (DIN) may progress toward invasive carcinoma with an increased risk. However, it is not fully understood whether DIN is polyclonal or monoclonal. In this current study, we detected clonal origin of DIN using x-inactivation at the human androgen receptor (HUMARA) locus. Lesional and normal breast gland cells were microdissected from paraffin-embedded tissues using a laser capture microdissection system. Genomic DNA was extracted. After digestion by restriction enzyme Hpa II, the HUMARA exon1 was amplified by a fluorescent nested-PCR procedure and the PCR products were separated on DNA sequencer and analyzed the fluorescent intensity of the two HUMARA alleles. DNA from 88 of 101(87%) patients was able to be amplified at the HUMARA locus and 68 of them (77.3%) were heterozygous and informative. 9/12 usual ductal hyperplasia (UDH) and 5/18 DIN 1A showed a polyclonal inactivation. 3/12 UDH, 13/18 DIN 1A, 28/28 DIN 1B, 10/10 carcinoma in situ are of monoclonal origin. Taken together, DIN 1A, 1B and carcinoma in situ, are monoclonal and DIN 1, but not UDH, represents the obligate and direct precursor of DCIS.