Microscopic examination of immunostains shows no nuclear staining for estrogen receptor (ER) or progesterone receptor (PR), and no membranous HER2 expression (score 0). Internal control elements are non-reactive, while the external positive controls show appropriate staining, confirming satisfactory assay performance and supporting the interpretation that the negative results are not attributable to technical or laboratory error.
Referred paraffin block for immunostaining of left breast mass diagnosed as invasive carcinoma (NST) grade 2 (pathology number 4399-2026 on 1 July 2026).
One referred paraffin block.
Left breast mass, immunostaining:
Comment:
External positive controls are satisfactory. In view of the non-reactive internal control elements, the negative immunostaining results should be interpreted with caution. Repeat immunohistochemical staining on an alternative tissue block may be considered if clinically warranted.