Which staining method is considered a connective tissue stain?

• A. Masson Trichrome
• B. Phosphotungstic acid-hematoxylin
• C. Verhoeff-van Gieson
• D. Oil Red O

Answer: (A)

Connective tissue stains are used to highlight collagen, a main component of the extracellular matrix. Masson Trichrome is the classic method for this purpose because it differentiates collagen from other tissue components by coloring collagen blue/green while staining muscle and cytoplasm red and keeping nuclei dark. This clear contrast makes connective tissue, such as fibrotic areas, easy to identify and measure. Other stains have different targets: phosphotungstic acid-hematoxylin emphasizes fibrin and muscle fibers rather than collagen; Verhoeff-van Gieson highlights elastic fibers (with collagen counterstaining); Oil Red O stains lipids in frozen sections and isn’t used for general connective tissue visualization. So, Masson Trichrome best fits the idea of a connective tissue stain.