Overview of Tissue Imaging Methods

The rapidly evolving fields of precision medicine and immuno-oncology are together driving an increasing need for detailed investigation of the tumor immune microenvironment (TIME) in a variety of solid tumors and hematologic neoplasms. The development of targeted therapies that may be efficacious in reprogramming the host immune response to recognize and eliminate tumor cells requires accurate identification of the various inflammatory cells and the spatial relationships between them within the TIME. While currently established techniques enable diagnostic pathologists to routinely interrogate for up to two protein markers and evaluate their expression by visual examination, there is a growing need to reliably query many more targets (i.e., multiplexing) simultaneously in a given tissue specimen, in order to more precisely characterize and distinguish the TIMEs between different tumor types, and between patients. Several technologies aimed at achieving these goals, including multiplex colorimetric immunohistochemistry (mCIHC), multiplex immunofluorescence (mIF), cyclic immunofluorescence (CycIF), multiplexed ion beam imaging (MIBI), codetection by indexing (CODEX), and digital spatial profiling (DSP), are discussed.