12
Diagnosis
Figure 3. Internal Controls
A B
C D
Figure legend: Examples of internal control analysis in ER stains. Panel A (200×)
illustrates an ER negative invasive cancer with an adjacent internal normal duct control (*)
with optimal staining (nuclear staining varying from weak to very strong with alternating
clusters of negative cells). Panel B (200×) is an example of an unexpectedly weak stain
result in both the grade 1 invasive cancer and the normal duct internal controls (*). is
result, although positive, raises concern about possible pre-analytic variables effecting the
assay or, if these are deemed appropriate, that at the level of analytic sensitivity of the assay
may be too low (especially to detect ER Low Positive results). Panel C (400×) is negative
for ER expression both in the in the invasive cancer and the internal control duct (*) .
e assay should be repeated and a investigation for potential causes of negative internal
controls performed (including both pre-analytic and analytic factors). If internal controls
remain negative and this issue appears isolated to this sample, the test should be reported
as "Cannot be determined" (indeterminate; uninterpretable due to negative internal
controls, possible pre-analytical tissue preservation issues). Panel D (200×) shows an
invasive cancer with no ER staining and internal control columnar cell epithelium (*) with
uniformly strong nuclear staining (as expected). ese results help support that there were
no serious issues with the pre-analytical and analytic phases. However, such strong positive
internal controls are less optimal to evaluate how well the assay is able to detect low levels
of ER expression (evaluation of non-columnar cell, normal duct controls is more optimal,
as in Panel A).
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