Among the listed options, the technique shown in the image is most likely which?

• A. Schmorl technique for reducing substances
• B. PAS
• C. Alcian blue pH 1.0
• D. Colloidal iron

Answer: (D)

Colloidal iron staining binds iron-containing colloid to the negatively charged groups of acidic mucopolysaccharides (carboxyl and sulfate) in tissue. This produces a distinct blue staining in areas rich in acidic glycosaminoglycans, such as mucins and basement membranes, making those substances visibly electrical blue under the microscope. The image likely shows this characteristic blue deposition pattern, which is different from what other stains depict: reducing-substance techniques highlight reducing sugars through copper-based reactions, PAS colors carbohydrates like glycogen and mucosubstances magenta, and Alcian blue at pH 1.0 specifically stains sulfated mucosubstances while pH 2.5 stains both sulfated and carboxylated mucosubstances. The staining pattern in the image aligns with the iron-colloid method, so this technique is the best match.