Tag Archives: ER

Breast – Predictive Markers

One of the most important aspects of breast cancer diagnosis is the evaluation of therapeutic markers (ER, PR, and HER2).  Ki-67 is often included in the panel as a prognostic marker.  ER expression determines eligibility to receive hormonal therapy (Tamoxifin), PR expression is a prognostic marker, and HER-2 over-expression determines eligibility to receive Herceptin®.  Diagnostically, the challenge is to consistently and accurately perform and interpret these IHC markers.
 
Estrogen Receptor (ER):
  • Nuclear Marker
  • Stain is reported as PERCENT STAINING OF TUMOR CELLS and STAIN INTENSITY (1+, 2+, 3+).
  • 1% or greater nuclear expression in tumor cells is considered positive, and therefore eligible to receive hormonal therapy.
  • CAP-ASCO recommendations are for <1 hr. from time of excision/biopsy to having a cut edge of tumor in 10% neutral bufferedormalin fixative.  Fixation window of 6-72 hrs.  These times should be noted in the pathology report (time of excision, time in gross room, and time in fixative).
  • Negative staining results in biopsy material without an internal control should be repeated on the excisional specimen using blocks with both tumor and benign breast parenchyma.
Progesterone Receptor (PR):
  • Nuclear Marker
  • Stain is reported as PERCENT STAINING OF TUMOR CELLS and STAIN INTENSITY (1+, 2+, 3+).
  • 1% or greater nuclear expression in tumor cells is considered positive.
  • PR expression is a prognostic marker, and not directly used for eligibility to receive a specific treatment.
  • PR expression without ER expression should raise significant concern that the ER and PR slides have been mixed up, or there is a problem with the ER assay.  Many scientists believe that ER expression is required for PR expression.
HER-2 Overexpression (HER-2):
  • Membraneous stain
  • Stain is interpreted by combining stain intensity and percentage of tumor involvement to classify as (0, 1+, 2+, or 3+).
    • 0 (negative) = No staining or cell membrane staining in <10% of tumor cells.
    • 1+ (negative) =  Faint membrane staining (partial membrane staining) in >10% of tumor cells.
    • 2+ (equivocal) =  Weak to moderate complete membrane staining in >10% of tumor cells, or strong complete staining in <10% of invasive tumor cells.
    • 3+ (positive) =  Strong complete membrane staining in >10% of tumor cells.
  • CAP-ASCO recommendations are for <1 hr. from time of excision/biopsy to having a cut edge of tumor in 10% neutral buffered fomalin fixative.  Fixation window of 6-72 hrs.  Over-fixation is probably not a clinically significant issue practically, but given the absence of relevant IHC data and the highly regulated environment surrounding HER2 testing, f/u FISH testing for negative results (outside the fixative window) is necessary.
  • Equivocal (2+) results should be followed-up with FISH testing, if IHC is used as the initial testing modality (most common).  Less than 1/3rd of equivocal cases show Her2 over-expression by FISH analysis.

References
 
Hammond ME, et. al.  “ASCO-CAP Guideline Recommendations for IHC Testing of ER and PR in Breast Cancer”.  Arch Pathol Lab Med-Vol. 134, June 2010.
 
Wolff, A. C., Hammond, M. E. H., Hicks, D. G., Dowsett, M., McShane, L. M., Allison, K. H., et al. (2013). Recommendations for Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Update. Archives of pathology & laboratory medicine. doi:10.5858/arpa.2013-0953-SA 
 
Tafe, L. J., Janjigian, Y. Y., Zaidinski, M., Hedvat, C. V., Hameed, M. R., Tang, L. H., et al. (2011). Human epidermal growth factor receptor 2 testing in gastroesophageal cancer: correlation between immunohistochemistry and fluorescence in situ hybridization. Archives of pathology & laboratory medicine, 135(11), 1460–1465. doi:10.5858/arpa.2010-0541-OA 
 
Arch Pathol Lab Med. 2001;125:746.

Breast – Normal IHC Expression

Normal breast ducts and lobules are lined by a 2-cell layer composed of luminal and myoepithelial cells.  There are also interspersed “basal” cells, which probably represent the epithelial progenitor cells.
 
IHC Marker
Luminal Cells
Myoepithelial Cells
LMWCKs
(CK7/8/18)
Positive
Negative
Variable Expression
Negative
HMWCKs
(CK5/14/17)
Negative
Positive
SMA
Negative
Positive
Negative
Positive
Negative
Positive
SMA=Smooth Muscle Actin, SMM-HC=Smooth Muscle Myosin Heavy Chain
 
An understanding of the normal IHC expression pattern in breast ductal tissue is important when considering IHC use in the differential diagnosis of breast pathology.

References
Hicks DG. Immunohistochemistry in the diagnostic evaluation of breast lesions. Appl Immunohistochem Mol Morphol. 2011;19(6):501–505. doi:10.1097/PAI.0b013e31822c8a48.
 
Liu H. Application of immunohistochemistry in breast pathology: a review and update. Arch Pathol Lab Med. 2014;138(12):1629–1642. doi:10.5858/arpa.2014-0094-RA.