Technical slide-preparation guidance for trained laboratory professionals — not a diagnostic opinion. Work back through the workflow and correct the earliest likely cause first. Validate all actions against your own SOP.
Tissue processing defects
Defect
Usually starts at
Likely causes
First action
Under-processed (soft/wet) tissue
Fixation / processing
Inadequate fixation before processing; Tissue cut too thick; Exhausted reagents; Schedule too short
Check fixation and thickness; rotate/replace reagents; use an appropriate schedule.
Over-processed (hard/brittle) tissue
Processing
Excessive time / long hold; Small biopsies on a routine cycle; High paraffin/oven temperature
Shorten schedule or avoid long holds; use a biopsy program; verify temperatures.
Embedding defects
Defect
Usually starts at
Likely causes
First action
Wrong tissue orientation
Embedding
Orientation technique not followed; Inadequate cold-plate setting
Re-embed on the correct plane; mark orientation at grossing; use a reference chart.
Air bubbles / voids in block
Embedding
Paraffin too cool when embedding; Turbulent / fast pour
Embed with fully molten paraffin at correct temperature; pour gently.
Microtomy defects
Defect
Usually starts at
Likely causes
First action
Chatter (thick–thin bands)
Processing / microtomy
Block too hard / over-processed; Dull blade; Loose clamp; Wrong clearance angle