What microtomy problem is most likely when sectioning the block shown?

• A. Difficulty forming ribbon
• B. Tissue tearing
• C. Sections curling
• D. Knife chatter

Answer: (A)

The key idea here is that forming a clean ribbon depends on the tissue and paraffin behaving cohesively as you cut. When the block causes trouble with ribbon formation, you’re seeing a failure of successive sections to detach and slide off as one continuous strand, instead producing broken or separated pieces.

In the shown block, the most likely issue is that the paraffin/tissue state isn’t ideal for clean consecutive sections—often because the block is too cold or infiltration was incomplete, making the wax or tissue too rigid. That rigidity causes the sections to fracture or not release neatly, so you don’t get a smooth ribbon. To fix it, adjust cutting temperature (warm the block slightly if needed), verify proper infiltration and paraffin quality, and ensure the blade and angle are appropriate.

Other problems have different signs: knife chatter shows blade vibration and rough edges, sections curling show curling due to moisture or bath temperature, and tissue tearing shows ragged edges from a very hard tissue or a dull blade.