One for all: HER2 guidebook for solid tumors
September 2026—Though it may test the memory of many, there once was a time when HER2 immunohistochemistry was a relatively uncomplicated matter. Back in September 1998, the FDA approved both trastuzumab (Herceptin) and the first companion diagnostic assay, HercepTest, which was used to determine whether patients with metastatic breast cancer could receive the new drug.