What is the most common method used for processing a specimen?

Formalin is the most common method used for processing a specimen due to its efficacy in preserving tissue for histological examination. When specimens are immersed in formalin, the formaldehyde in the solution reacts with the proteins in the tissue, effectively cross-linking them. This process helps to maintain the architecture of the tissue and prevents the decay of biological material, providing a stable sample for evaluation under a microscope.

Formalin fixation allows for detailed examination of cellular and structural details, which is crucial for diagnostic purposes. After fixation, the tissue can be further processed and embedded in paraffin, but formalin serves as the initial and critical step in the preservation process.

While alcohol, acetone, and paraffin are involved in various aspects of specimen processing, they do not serve as the primary fixative like formalin does. Alcohol is often used for dehydrating tissues, acetone serves similar roles but is less common, and paraffin is primarily a medium for embedding after fixation has already taken place. Thus, formalin is the cornerstone of tissue processing, making it the most common method used.