Immunohistochemical Profile in Invasive Ductal Carcinoma of the Breast

Mandatory Markers

The American Joint Committee on Cancer recommends that the standard immunohistochemical profile for invasive ductal carcinoma of the breast should include estrogen receptors (ER), progesterone receptors (PR), and HER2, as determined by immunohistochemistry, as these markers are essential for therapeutic planning and prognosis 1, 2, 3
The determination of ER and PR is mandatory in all samples of invasive ductal carcinoma, preferably by immunohistochemistry, and the result is reported as positive if ≥1% of tumor cells show nuclear staining of any intensity 2, 4
The percentage of cells with nuclear staining and the average intensity (strong, moderate, or weak) should be reported 2
Hormone receptors are the most relevant predictive factor for treatment choice, although they are no longer considered prognostic factors according to the St Gallen Consensus 3

The determination of HER2 should be performed simultaneously with ER/PR in all cases of newly diagnosed invasive carcinoma 1, 3
HER2 can be evaluated by immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH) 1, 3
When IHC results are ambiguous (++), FISH or CISH should be performed to determine HER2 gene amplification 3, 4
The method used should be validated and show ≥95% concordance with another validated method 1

The tissue should be oriented adequately for the pathologist with sutures or other markers 1, 5
Relevant clinical history, including laterality (right or left breast) and quadrant, should be provided 1, 5
Internal and external controls should react appropriately before reporting patient results 2
If controls do not produce the expected reaction, the result should not be reported and the assay should be repeated 2