Fixation with NBF will cause tissue cytoplasm to take up more hematoxylin.

• A. Yes
• B. No
• C. Sometimes
• D. Never

Answer: (A)

Neutral buffered formalin fixation preserves and crosslinks cellular components in a way that can enhance basophilic regions beyond the nucleus. Hematoxylin is a basic dye that binds to acidic, basophilic structures such as nucleic acids and ribonucleoprotein complexes. In many cells, the cytoplasm contains RNA-rich regions (like abundant ribosomes and rough endoplasmic reticulum) that are basophilic. When tissue is fixed with NBF, these cytoplasmic basophilic components are well preserved and become more accessible to hematoxylin, so the cytoplasm can take up more hematoxylin than it would without fixation. This is tissue- and condition-dependent, but it explains why the cytoplasm might appear more blue/purple after formalin fixation in some specimens.