Which fixative is the choice if a specimen will not be processed for several days?

• A. 10% neutral buffered formalin
• B. 70% alcohol
• C. Zenker solution
• D. Helly solution

Answer: (A)

When a specimen may sit unprocessed for several days, you need a fixative that reliably preserves tissue structure and remains compatible with downstream processing. Ten percent neutral buffered formalin fits this role best because it cross-links proteins to halt enzymatic degradation and maintain microscopic morphology, while its neutral pH avoids artifacts that can interfere with staining. This fixation method is routine for surgical specimens and pairs well with paraffin embedding, so tissues fixed in it can be handled later without special steps.

alternatives like 70% alcohol don’t provide the same level of preserved architecture for long delays; they dehydrate and can cause shrinkage or hardening, which complicates later processing and interpretation. Fixatives such as Zenker or Helly are more hazardous and require additional, specialized handling and steps, making them impractical for a backlog of specimens. Thus, the standard choice for a specimen delayed in processing is ten percent neutral buffered formalin.