Progesterone Receptor (PR)

Sample for Progesterone Receptor (PR)

• The paraffin blocks of the breast cancer tissue are needed for the cytochemical method.
  • There are immunocytochemical and immunochemical methods.

Purpose of the test (Indications) for Progesterone Receptor (PR)

1. PR is done to see the sensitivity to anti-hormone therapy in the case of breast cancers.
2. PR gives the prognosis of breast cancer.

Pathophysiology of Progesterone Receptor (PR)

1. Progesterone receptor is a specific cellular protein with high affinity and specificity for progesterone hormone.
2. The progesterone receptor protein is found in the target tissue like the breast, uterus, pituitary gland, and hypothalamus.
3. Progesterone stimulates the cells through the progesterone receptor.
4. A reduction in the blood progesterone level reduces the biochemical activity of this cell.
   1. This is the basis for the treatment of breast cancer by antihormone therapy,
   2. PR-positive breast cancer is more responsive than PR-negative cases.
5. Postmenopausal women’s breast cancers are more PR positive than young women.

6. Mechanism of the anti-hormone therapy where the drug blocks the site of Progesterone hormone, and there is no signal for cell proliferation.

Reading of the immunocytochemistry slides:

• PR receptor stain in the nucleus (the color is brown).
  • Negative = < 5 % of the cells are positive for the PR receptors.
  • Positive = > 5 % of the cells stain for the PR receptors.

Clinical evaluation for PR receptor-positive breast cancer:

• Carcinoma of the breast shows 60 %  positivity.
• Approximately 2/3 of the cases show a response to hormone therapy.
• PR negative cases, 90% do not respond to hormone therapy.

Response to anti-hormone therapy

Questions and answers: