What % is negative??

I found this interesting 'cheat sheet'.  Not that it answers your question but it does go into a fair amount of detail about receptors.

http://palpath.hypermart.net/MedicalTestPages/brcaprls.htm

It is my understanding that and ER or PR of 10% or greater would suggest possible benefit from hormonal therapy. 

According to  http://breastcancer.about.com/od/diagnosis/p/hormone_status.htm

 Estrogen and Progesterone Status Affects Diagnosis & Treatment of Breast Cancer: Estrogen and Progesterone biomarker tests results will appear on your pathology report. Understanding the test results is important, because this information affects your treatment as well as your follow-up care, if you've been diagnosed with breast cancer.
Why you need to know your hormone status: Estrogen and Progesterone receptor status tests will show whether or not one or both of those hormones fuel your tumor. Cancer that is hormone-sensitive is slightly slower growing and has a better chance of responding to hormone-suppression treatment, than cancer that is hormone receptor negative. Hormone-negative cancer will respond to other kinds of treatment, and hormone-suppression may not be needed.
Positive vs. Negative Estrogen Status: A score of Estrogen Receptor positive (ER+) means that estrogen is causing your tumor to grow, and that the cancer should respond well to hormone suppression treatments. If the score is Estrogen Receptor negative (ER-), then your tumor is not driven by estrogen, and your results will need to be evaluated along with other tests, such as your HER2 status, to determine the most effective treatment.
Positive vs. Negative Progesterone Status: If you get a Progesterone Receptor positive (PgR+ or PR+) score, the cancer should respond well to hormone suppression treatments. If the score is Progesterone Receptor negative (PgR- or PR-), then your tumor is not driven by progesterone, and another test is needed, for your HER2 status, to determine the most effective treatment. HER2 positive breast cancer responds well to Herceptin treatment.
When should you ask for a numerical score?: If your hormone status tests are scored only as negative, it is good to ask your doctor for a number that indicates the actual score. Even if the number is a low one, these kind of cancers may effectively be treated with hormone therapy.
Scores on these tests: On your pathology report, you may see the scores for Hormone Status. This is expressed as a number between 0 and 3. Here's how to understand the numbers:

* 0 is no receptors found,
* 1+ is a small number,
* 2+ is a medium number, and
* 3+ is a large number of receptors.

What is the percent of hormone receptors?: You may also find the number of cells out of 100 cells that tested positive for hormone receptors. This is written as a number between 0% (no receptors) and 100% (all cells have receptors).
What is the treatment?: Anti-estrogen therapy works by blocking the hormone receptors, so they can't signal cancer cells to grow. Some of the drugs that are widely used to treat hormone-receptor positive cancers are:

* Tamoxifen
* Raloxifene
* Arimidex (chemical name: anastrozole),
* Aromasin (chemical name: exemestane), and
* Femara (chemical name: letrozole)
* Faslodex (chemical name: fulvestrant)

How is the test done?: Unlike a blood test for estrogen, which helps to determine your menopausal status, this test does not use a blood sample. After your biopsy, a thin sample of the tissue will be examined and tested under a microscope.