SORTING OUT MIX-UPS - THE PROVENANCE OF TISSUE-SECTIONS MAY BE CONFIRMED BY PCR USING MICROSATELLITE MARKERS

Standard identification systems usually ensure that biopsy material is correctly associated with a given patient, Sometimes, as when a tumor is unexpectedly found, the provenance (proof of origin) of a tissue s ample may be questioned; the tissue may have been mislabelled or conta minated with tissue from another patient. Techniques used to confirm t issue provenance include comparing either tissue markers of gender or ABO blood groups; however, these methods have weak confirmatory power, Recently, the use of DNA-based polymerase chain reaction (PCR) techni ques has been reported. Paired, formalin-fixed, paraffin-embedded, 10 mu m tissue sections were selected from 17 patients, 8 of whom had car cinoma, either by dividing a biopsy section, using sequential biopsies , or sequential biopsy and autopsy tissue. The resulting 36 samples we re coded before analysis. In two additional cases, l-mm fragments of t umor from one patient were included in the tissue block of benign tiss ue from another patient, the tumor fragments were identified on hemato xylin-and-eosin-stained sections, separately scraped off the glass sli de, and analyzed, Tissue from two clinical cases, one of suspected mis labelling and one with a suspected carry-over of malignant tissue were also investigated, Short tandem repeat sequences (STR) or microsatell ites, are 2-5 base pair repeats that vary in their repeat number betwe en individuals, This variation (polymorphism) can be assessed using a PCR, A panel of markers of 3 STRs; ACPP, INT 2, and CYP 19 (on chromos omes 3, 11, and 15, respectively) were used. DNA was isolated from til e samples after xylene deparaffinization and proteinase digestion, and was then amplified in a radioactive PCR using primers selected to giv e a product size ranging from 136-178 bases. Amplified products were e lectrophoresed on denaturing polyacrylamide gels, dried, and autoradio graphed. DNA segments were successfully extracted from all samples but one, which was fixed in Bouin's fluid, By comparing allele sizes from the panel, all tissue pairs (other than the Bouin's pair) were succes sfully matched, the 1-mm tumor fragments mere correctly assigned, and the two clinical problems were solved. STRs are highly informative and robust markers, well suited to PCR of small portions of tissue sectio ns, and are an effective method to confirm the provenance of benign an d malignant biopsy and autopsy material.