Which tissue component is used to demonstrate adipose cells?

• A. Oil red O
• B. Mast cells
• C. Masson trichrome
• D. Van Gieson

Answer: (A)

The key idea is visualizing lipids within fat cells. Oil Red O is a fat‑soluble dye that stains neutral lipids red, so the large lipid droplets inside adipocytes become clearly visible against a counterstain. Because routine paraffin processing dissolves lipids, this stain is typically used on frozen sections (or after fixation methods that preserve lipids, like osmium tetroxide). That combination makes adipose cells easy to identify by the characteristic red droplets with the nucleus pressed to the cell edge. The other stains highlight different tissue components—collagen or muscle with Masson trichrome or Van Gieson, and mast cells require other specialized stains—so they don’t specifically reveal adipose lipids.