If a tissue block indicates the specimen was not centered in the mold, what should have been done?

• A. The tissue should have been centered in the mold
• B. The tissue should have been oriented incorrectly
• C. The tissue should have been placed in a too-hot mold
• D. The tissue should have been fixed longer

Answer: (A)

Centering the tissue in the mold is essential so that it is completely enveloped by paraffin and positioned near the block’s center. When a specimen is off-center, there’s uneven wax around it, which makes sectioning difficult and can produce ribbons with variable thickness, tissue near the surface or edge artifacts, and potential tissue loss. By placing the tissue in the center before the paraffin solidifies, you ensure consistent orientation and easier, cleaner microtomy. If the block shows it wasn’t centered, re-embed the tissue in a new mold with the specimen centered to achieve a properly formed block.