Underfixation consequences?

• A. Autolysis, tissue soft and mushy, loss of antigenicity
• B. Tissue hard and shrinks
• C. No effect on tissue quality
• D. Increased coloration

Answer: (A)

Underfixation lets endogenous enzymes keep working after tissue is fixed, so autolysis begins and tissue preservation deteriorates. This enzymatic degradation softens the tissue, making it mushy, and also alters or destroys antigenic sites, leading to loss of antigenicity and weaker immunohistochemical staining. Fixatives work by cross-linking proteins to halt these processes; when fixation is insufficient or penetration is incomplete, preservation is poor. You won’t see harder, shrunken tissue or enhanced coloration from underfixation; those effects are more typical of overfixation or other processing issues.