H&E stained slides reveal brown pigment-like stippling and rare glossy black nuclei. This is most likely caused by mounting medium that was applied after letting the slide dry. Correction would be which of the following?

• A. Mounting medium applied after drying
• B. Inadequate differentiation of hematoxylin
• C. Too much heat during processing
• D. Poor dehydration

Answer: (A)

The main idea here is how mounting technique affects what you see under the microscope. When mounting medium is applied after the slide has dried, the medium can crystallize or dry in a way that traps air and creates surface deposits. That can look like brown pigment-like stippling on the tissue and makes nuclei appear unusually glossy or dark under the coverslip. So the observed pattern points to a mounting-step issue: the mounting medium was not used at the proper stage of slide preparation, which disrupts how light passes through the stained tissue and alters appearance.

In contrast, inadequate differentiation of hematoxylin would change nuclear color consistency, not produce these brown speckles and glossy nuclei. Excessive heat during processing tends to cause tissue damage and abnormal staining overall, while poor dehydration leads to poor clearing and a milky or fragmented appearance. Those problems don’t specifically explain the combination of brown stippling and glossy nuclei seen here.