A Guide to IHC

How immunohistochemical analysis can help navigate the complexities of breast pathology

By Ping Tang
June 2016

At a Glance

  • Our increasing knowledge of the diverse nature of breast cancer is giving rise to ever more diverse tests
  • While molecular tests are increasing in importance, immunohistochemistry (IHC) analysis is just as useful in the differential diagnosis of breast lesions as well as for prognosis and prediction 
  • IHC can also be used as a tool in the discovery of new therapeutic targets, and in combination as a surrogate for molecular classifications and multigene prognostic panels
  • Here, I provide a guide to how IHC analysis can help pathologists make a correct diagnosis and provide accurate prognostic and predictive information to clinicians, and to inform of the factors that might impact IHC test quality

The more we learn about breast cancer, the more we realize just what a broad classification it truly is. Despite what many patients still believe, there’s no one “breast cancer” to rule them all – it’s a heterogeneous group of tumors, and each type exhibits different characteristics, different behaviors and different clinical outcomes. As a result, we’re parlaying this increase in understanding into ever more diverse tests to gain insight into the nature of each individual patient’s disease – and although genomics is an up-and-coming field of study, the molecular tests aren’t the only ones that play a role in tumor classification (1). Immunohistochemistry (IHC) plays an important part too.

Traditionally, IHC analysis has been used for diagnosis in difficult cases, but more recently it has served as a prognostic or predictive marker, as a tool in the search for new therapeutic targets, and even in combination as a surrogate for molecular classifications and multigene prognostic panels. But with a wide range of biomarkers available for IHC testing, it’s important for pathologists to understand what’s out there, how it can be used, and where things might go wrong.