Diagnosis of uncertain primary tumors with the Pathwork tissue-of-origin test.

Clinical workup of metastatic malignancies of unknown origin is an arduous and expensive process, which is reported to be unsuccessful in up to 30% of cases. Global gene expression-based molecular testing may offer accurate classification of metastatic tumors in which a primary site has not been identified. Recently, the US FDA cleared the Pathwork((R)) tissue-of-origin test, which is a gene expression microarray-based test that quantifies the molecular similarity of tumor specimens to 15 known tissue types. A blinded, multicenter validation on poorly differentiated and undifferentiated tumors showed 87.8% sensitivity and 99.4% specificity in frozen tissue samples. The availability of ancillary gene expression-based molecular tests for tissue of origin determination represents a milestone in cancer patient management as part of the personalized medicine revolution.