Type of test Microscopic examination
Normal findings
Immunohistochemistry
Negative: < 5% of the cells stain for receptors
Positive: > 5% of the cells stain for receptors
Reverse-transcriptase polymerase chain reaction (RT-PCR)
Negative: < 6.5 units
Positive: > 6.5 units
Test explanation and related physiology
The ER assay is useful in determining the prognosis and treatment of breast cancer. The assay is used to determine whether a tumor is likely to respond to endocrine therapy. Tumors with a positive ER assay are more than twice as likely to respond to endocrine therapy than ER-negative tumors.
Interfering factors
• Delay in tissue fixation or too long in fixative solution may cause deterioration of receptor proteins.
Procedure and patient care
Before
* Explain the procedure to the patient.
* Instruct the patient to discontinue hormones before breast biopsy is performed. Verify with the physician.
During
• The surgeon obtains tumor tissue.
• Part of the tissue is used for routine histology. A portion of the paraffin block or a slide containing cancer is used for immunohistochemistry (IHC) staining.
After
• Results are usually available in 1 week.
Abnormal findings
Not applicable
