In Masson's trichrome with aluminum Hematoxylin, what color do the nuclei appear?

• A. Red - same as cytoplasm
• B. Blue
• C. Green
• D. Purple

Answer: (A)

Masson's trichrome separates color by using three dyes: a nuclear stain, a cytoplasmic/muscle stain, and a collagen stain. When aluminum hematoxylin is used as the nuclear stain, the nuclei take on a reddish hue instead of the blue-black color you’d expect with iron hematoxylin. After the rest of the staining steps, this red nuclear color remains distinct and ends up appearing the same color as the cytoplasm, which is also red. So the nuclei appear red, matching the cytoplasm. If a blue or purple nuclear stain were used instead, the nuclei would look different from the cytoplasm.