Clinical Information
Beyond IHC

Limitations of current technologies: Traditional diagnostic approaches for challenging cancer cases usually involve multiple rounds of imaging and several types of immunohistochemical analysis (IHC), which are time-consuming because of the complex iterative process they may require. They are costly and often do not produce a definitive diagnosis.

More advanced diagnostic tools available to clinicians today include cytogenetic studies, and imaging procedures such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). However, in the case of difficult-to-classify tumors, even advanced technologies identify the tumor origins in only about 20% to 25% of the time.2


  • Immunohistochemical Analysis (IHC) is a type of assay in which antigens are visualized using antibodies followed by fluorescent dye or enzyme markers. Pathologists use various combinations of dyes to identify the tissue of origin of a tumor. However, IHC depends on subjective visual evaluation, may differ between laboratories and may lack the specificity and sensitivity to address the full range of potential tumor types. 3 One study showed that IHC was only 66% accurate at identifying the primary site of metastatic tumors.5 In addition, currently available IHC markers do not address the full range of potential tumor types, and the most commonly used stains (CK7 and CK20) produce false positives and false negatives frequently enough to make a definitive diagnosis difficult.6 Thus, IHC studies alone may not provide enough information to definitively identify the primary tumor site.
  • Cytogenetic studies, which assess chromosomal abnormalities, can provide insights in a number of specific tumor types. However, this technique is limited because only a few diagnostic chromosomal abnormalities have been identified to date.7
  • Imaging techniques have been valuable tools in the assessment of patients with ambiguous or hard-to-classify tumors. CT, MRI, and PET scans can all be helpful. These various imaging techniques may pinpoint the anatomic location and characteristics of the tumor, but may not confirm the origin of the tumor.