Endomyocardial biopsy samples are placed in which fixative before laboratory analysis?

• A. Formalin
• B. Formaldehyde solution
• C. Saline
• D. Ethanol

Answer: (A)

Fixation preserves tissue morphology by cross-linking proteins and halting enzymatic degradation, which is essential for accurate histology. For endomyocardial biopsy, the standard fixative is formalin, typically 10% neutral buffered formalin. This choice preserves cardiac tissue well and is compatible with paraffin embedding and routine stains like H&E as well as immunohistochemistry. Saline doesn’t fix tissue, so it doesn’t protect structure. Ethanol can fix but tends to cause dehydration and shrinkage, altering morphology. Formaldehyde solution is essentially the same chemical, but the common, standardized term used in pathology is formalin. Therefore, the sample is placed in formalin.