Gene expression profiling from formalin-fixed, paraffin-embedded tissue for tumor diagnosis

Molecular profiling assays have emerged as a promising tool in tumor diagnosis. Recent advances have allowed the use of formalin-fixed, paraffin-embedded (FFPE) tissues in such assays involving the use of microarrays. The Pathwork Tissue of Origin (TOO) Test was developed for use with FFPE tissue to aid tumor diagnosis. We sought to determine the performance of the TOO test on routine specimens from an independent laboratory.Forty-five blinded, archived clinical specimens from the UCSF Department of Pathology were tested. Total RNA was processed to prepare labeled cDNA for hybridization to Pathchip microarrays. Hybridization data was analyzed with a 2000-gene classification model to quantify similarity between RNA expression of the study specimens and the 15 tissues on the test panel.44/45 (98%) specimens were successfully processed. 37 cases met study inclusion criteria. Of these, 35 (95%) gave results which were in agreement with the reference diagnosis. In no case was the reference diagnosis ruled out.The Tissue of Origin Test gave a high agreement with the reference diagnosis when archived clinical specimens from UCSF were assessed. Molecular profiling assays are highly accurate, and can be a useful tool in cancer diagnosis.