Overheating during paraffin infiltration (2-4 C above the melting point) leads to tissue that is

• A. Hard and shrunken
• B. Soft and swollen
• C. Discolored
• D. Mottled

Answer: (A)

Overheating during paraffin infiltration accelerates the exchange between tissue and infiltrant, driving excessive dehydration. As water and some lipids are removed more than normal, the tissue matrix collapses and the embedded specimen becomes denser. The result is a hard, shrunken tissue that can fracture or distort during sectioning and staining.

Soft and swollen would imply excessive fluid uptake or insufficient dehydration, which isn’t the typical outcome of overheating. Discolored or mottled appearances are more about pigment damage or uneven infiltration, not the primary morphological change caused by overheating.