History of Testing for HER2: Timeline

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History of Testing for HER2: Timeline

  • Western blot: Used on homogenized tissue in the late 1980s.
  • Southern blot: Gene amplification was initially detected by Southern blot in frozen tumor specimens and was subsequently found to correlate with overexpression at the mRNA and protein levels.
  • Enzyme-linked immunosorbent assay (ELISA): This was used on homogenized tissue or blood in the late 1980s, mid-1990s, and mid-2000s.
  • Immunohistochemistry (IHC): This technique is used on tissue sections, first on frozen sections and later on paraffin sections. Several clones have been used over the years, such as clone 4D5 and clone CB11, with vast improvements in recent years owing to the standardization of IHC.
  • Fluorescence in situ hybridization (FISH): Used on tissue sections in the early 2000s.
  • Digital image analysis (DIA): Used in combination with IHC and ISH as a scoring method for HER2 status after 2015. It provides an objective alternative to manual scoring, but a reduction in 2+ cases could result in loss of sensitivity.