The Pathwork Tissue of Origin Test for FFPE is a microarray-based gene expression test that aids in the diagnosis of poorly differentiated and metastatic tumors. A recent study of 284 clinical samples with Tissue of Origin Test results were categorized according to the clinician's pretest diagnosis, using ICD-9 codes and the biopsy site. The test predicted either a change from nonspecific to a specific site or a change from one primary site to another in 81% of cases. For 15% of cases, the Tissue of Origin Test confirmed the submitted diagnosis. Overall, based on test prediction and the NCCN guidelines, first-line chemotherapy treatment would change for 63% of the cases.
This test is FDA approved but how to use it is not clear. There are several other validation studies but clinical impact must be proven before it is accepted for wider use. On p. MS4 of its Occult Primary Guideline the NCCN does not recommend GEP (Genetic Expression Profiling) for routine evaluation.
At this time, it should still be considered investigational.
Laouri, M., Nystrom, J. S., Halks-Miller, M., Henner, W. D.
Impact of a gene expression-based tissue of origin test on diagnosis and recommendations for first-line chemotherapy.
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Monzon FA, Lyons-Weiler M, Buturovic LJ et al. Multicenter validation of a 1,550-gene expression profile for identification of tumor tissue origin. J Clin Oncol 2009; 27(15):2503-08.
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