Practice scoring HER2 IHC whole slide images

Not aligned with the Pathology Faculty score

This case shows membrane staining is incomplete and faint/barely perceptible in ≤10% of invasive tumor cells.

*According to the CAP Breast Biomarker Reporting Template, a score of IHC 0+ has membrane staining that is incomplete and is faint/barely perceptible and in ≤10% of tumor cells.¹

Not aligned with the Pathology Faculty score

This case shows weak to moderate complete membrane staining in >10% of invasive tumor cells.

Reflex ISH testing is required to determine HER2 amplification status. If ISH is negative, this case falls under “HER2 low” category per DESTINY-Breast trials and may be eligible for fam-trastuzumab deruxtecan-nxki in the metastatic setting.

Not aligned with the Pathology Faculty score

This case shows incomplete membrane staining that is faint/barely perceptible in >10% of invasive tumor cells, with focal weak to moderate complete membranous staining in ≤10% of tumor cells.

Not aligned with the Pathology Faculty score

This case shows no membrane staining detected in invasive tumor cells. Internal control (benign lobule) shows expected faint membranous staining, confirming assay performance.

This slide shows absent membranous staining throughout the invasive tumor cells. In evaluating such cases, it is critical to assess both internal and on-slide positive controls. In this case, a benign lobule with faint membranous staining on the left side of the specimen serves as an internal control. This case also requires careful distinction between invasive and in situ carcinoma.

Not aligned with the Pathology Faculty score

This case shows no membrane staining detected in invasive tumor cells.

This case highlights the importance of distinguishing invasive from in situ carcinoma, as only invasive tumor cells should be evaluated for HER2 membranous staining.

Not aligned with the Pathology Faculty score

This case shows circumferential membrane staining that is complete, intense, and in >10% of invasive tumor cells.

Not aligned with the Pathology Faculty score

This case shows incomplete membrane staining that is faint/barely perceptible in >10% of invasive tumor cells.

The invasive component involves a small portion of the tissue. Remaining tissue includes ductal carcinoma in situ and benign glandular elements. A duct with apocrine metaplasia shows granular cytoplasmic staining, which should not be interpreted as HER2 positivity. Careful distinction between invasive carcinoma and non-invasive elements is essential.

Not aligned with the Pathology Faculty score

This case shows circumferential membrane staining that is complete, intense, and in >10% of invasive tumor cells.

Not aligned with the Pathology Faculty score

This case shows weak to moderate complete membrane staining in >10% of invasive tumor cells, with areas of incomplete weak staining.

Reflex ISH testing is required to determine HER2 amplification status. If ISH is negative, this case falls under “HER2 low” category per DESTINY-Breast trials and may be eligible for fam-trastuzumab deruxtecan-nxki in the metastatic setting.

Not aligned with the Pathology Faculty score

This case demonstrates strong, complete circumferential staining in the invasive tumor cells.

Not aligned with the Pathology Faculty score

This case shows membrane staining that is incomplete and faint/barely perceptible in ≤10% of invasive tumor cells.

*According to the CAP Breast Biomarker Reporting Template, a score of IHC 0+ has membrane staining that is incomplete and is faint/barely perceptible and in ≤10% of tumor cells.¹

Not aligned with the Pathology Faculty score

This case shows incomplete, faint/barely perceptible membrane staining in >10% of invasive tumor cells. This case shows predominantly weak membranous staining in the invasive tumor cells.

Caution should be taken not to interpret luminal and/or granular cytoplasmic staining as positive membranous staining.

Not aligned with the Pathology Faculty score

This case shows membrane staining that is incomplete and faint/barely perceptible in ≤10% of invasive tumor cells (pattern consistent with HER2 ultralow).

*According to the CAP Breast Biomarker Reporting Template, a score of IHC 0+ has membrane staining that is incomplete and is faint/barely perceptible and in ≤10% of tumor cells.¹