What is the typical sequence of steps in FFPE processing from biopsy to mounted slide?

• A. Fixation in formalin, embedding, dehydration, clearing, paraffin infiltration, sectioning, mounting, and staining.
• B. Fixation in formalin, dehydration, clearing, paraffin infiltration, embedding, sectioning, mounting, and staining.
• C. Embedding, fixation, dehydration, clearing, paraffin infiltration, sectioning, mounting, and staining.
• D. Fixation in formalin, dehydration, clearing, staining, embedding, sectioning, mounting.

Answer: (B)

FFPE processing follows a preservation-to-analysis flow: fix the tissue in formalin to lock cellular structures in place, then remove water through graded dehydration with alcohols, followed by clearing with a solvent that makes the tissue ready to accept paraffin. After clearing, the tissue is infiltrated with molten paraffin so the tissue is saturated with paraffin, and then embedded in a paraffin block for solid support. The block is then sectioned on a microtome to produce thin slices, which are mounted onto slides. Finally, the mounted sections are stained to visualize cellular details under the microscope. This order ensures proper tissue preservation, adequate support for thin sectioning, and reliable staining results.