Molecular stability of DNA typing short tandem repeats in the mammary tree of patients with breast cancer.

Archival pathologic specimens are a rich source for the studies of hereditary diseases, cancer genetics, and identification cases in forensic science. In this study, the intraindividual consistency of eight identifying microsatellite polymorphisms (i.e., HMTH01, vWFA31, F13A, MITMH26, FES-FPS, CD4, TPOX, CSF1PO)in a cohort of 40 patients with invasive breast carcinoma were analyzed. Nests of cancer and adjacent morphologically normal ductal-lobular structures (TDLUs) were microdissected as discrete regions from hematoxylin-eosin-stained slides. As controls for each case, DNA templates were prepared from TDLUs located in nontumor quadrants and from unaffected breast skin. Over 1,400 carefully controlled PCR reactions were reviewed, and no evidence was found for microsatellite mismatches among intraindividual cancer and control DNAs. The negative results, supported by validation experiments, strongly argue that alterations of simple repeats are rare somatic events during the onset and progression of breast cancer. This study suggests that PCR artifacts may be a relevant cause of misdiagnosis of microsatellite instability in human sporadic cancer.