HDAC9 and neoplasm: For HRP HGSTOC, in order to explore effective therapies, we not only proposed that HDAC inhibitors (HDACis) may serve as an effective therapeutic strategy, which was validated by animal experiments, but also innovatively discovered the existence of a physical barrier formed by “indolent CAFs” surrounding tumor cells, confirmed by multiplex immunohistochemistry (mIHC), which might serve as a promising target.