Periodic Acid-Methanamine for Basement Membranes delineates which structure?

• A. Glomerular basement membrane
• B. Renal tubules
• C. Alveolar walls
• D. Basement membranes in general

Answer: (A)

Periodic acid–methenamine silver highlights basement membranes by depositing silver in the carbohydrate-rich matrix, yielding a sharp, dark outline wherever a basement membrane is present. In kidney tissue, the glomerular basement membrane forms a continuous, conspicuous outline around the capillary loops, so this stain most prominently delineates the glomerular basement membrane. This makes it especially useful for assessing GBM integrity, thickness, or irregularities in glomerular diseases. While basement membranes exist around renal tubules and alveolar walls, the characteristic, diagnostic highlight of this stain on histology slides is the glomerular basement membrane, not basement membranes in general.