Multiplex DNA short tandem repeat analysis. A useful method for determining the provenance of minute fragments of formalin-fixed, paraffin-embedded tissue.

A tiny fragment of high-grade carcinoma was found in histologic sections and in the paraffin block of a benign cervical polyp from a patient with no clinical evidence of malignancy. Thus, it raised the suspicion of block contamination. No malignant tumor was processed the same day as the polyp; however, a similar tumor had been processed 6 days earlier. Multiplex DNA short tandem repeat analysis was applied to paraffin-extracted tissue samples obtained from the polyp, the suspected contaminant, the patient's additional cervical biopsy specimen, and the putative source of contamination. The results demonstrated that the suspected contaminant and the patient's cervical tissue could not have come from the same patient and that the suspected contaminant derived from the tumor processed earlier, without reasonable doubt. We hypothesize that this friable tumor escaped from cassettes into the processor and contaminated the polyp specimen. Multiplex DNA short tandem repeat analysis can be applied to determine the provenance of minute tissue samples in surgical pathology.