Breast: Practice Question

Which of the following estrogen receptor (ER) profiles is reported as "low positive" in invasive breast cancer?
  1. 1 - 10% positive by IHC
  2. 0.5% positive by IHC
  3. 20% positive by IHC
  4. 0.1 - 1% positive by IHC
  5. 50% positive by IHC
Show Answer and Explanations

1 - 10% positive by IHC — Correct answer

Correct. Breast cancer samples with 1% to 100% of tumor nuclei positive are interpreted as ER positive. However, there may be limited benefit from endocrine therapy for cancers with 1% to 10% of cells staining ER positive. Data is limited but suggests a possible benefit, so patients are eligible for endocrine treatment. There are data that suggest invasive cancers with these results are heterogeneous in biology and behavior and often have gene expression profiles more similar to ER-negative cancers. These results should be reported using the reporting category "ER Low Positive". A sample is considered ER negative if < 1% or 0% of tumor cell nuclei are immunoreactive.

0.5% positive by IHC

Incorrect. A sample is considered ER negative if < 1% or 0% of tumor cell nuclei are immunoreactive.

20% positive by IHC

Incorrect. Breast cancer samples with 1% to 100% of tumor nuclei positive are interpreted as ER positive. 1 - 10% is considered "low positive".

0.1 - 1% positive by IHC

Incorrect. A sample is considered ER negative if < 1% or 0% of tumor cell nuclei are immunoreactive.

50% positive by IHC

Incorrect. Breast cancer samples with 1% to 100% of tumor nuclei positive are interpreted as ER positive. 1 - 10% is considered "low positive".

Summary

Summary: Invasive breast cancers with 1% to 10% of cells staining ER positive are categorized as "low positive" and may behave more like ER negative tumors, but there still may be some benefit from endocrine therapy.
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