Traditionally, the pathologist has relied on immunohistochemistry (IHC) to arrive at a conclusion when confronted with cancers of unknown primary or undifferrentiated malignancies. A relatively recent development is, however threatening to upstage this current modality of probing cancer histogenesis.
Studies using miRNA microarray or RT-PCR for gene expression profiling has yielded satisfactory results comparable to IHC. With a one-step procedure obviating the step-wise algorithm based approach of IHC, there is a serious question on the possible obsolescence of IHC in evaluating histogenesis. While early workers analyzed frozen sections, more recently, the successful use of archival formalin fixed paraffin embedded tissue has truly challenged the future of IHC.
Companies have begun to market this technology; despite Pathwork Dx which pioneered an FDA approved “Tissue of Origin” test having gone out of business in early 2013, others like BioTheranostics with its 92-gene based “CancerType ID” and Rosetta Genomics with the 64 microRNA based “Rosetta Cancer Origin Test” are likely to spearhead the technology in the future.
Whether gene expression studies will completely wipe out the need for IHC or; only provide supplemental assistance to the time-honored pink-and-blue slide reporting, needs to be seen.