Progesterone receptor (PgR or PR) immunohistochemistry (IHC) is a technique used to assess the expression of the progesterone receptor in breast cancer tissues.

The progesterone receptor is a hormone receptor that, when expressed, is associated with hormone-driven breast cancers, which tend to have a better prognosis. IHC staining for PR involves applying an antibody that binds to the progesterone receptor on the cell surface or within the nucleus, which is then visualized using a chromogen.

The staining is scored based on the percentage of tumor cells showing nuclear staining and the intensity of that staining, helping to determine PR positivity. This scoring is critical for evaluating eligibility for hormone therapies like tamoxifen.

PAIKON for IHC PR testing is currently availible as RUO product for microscopic and whole slide images.