Which staining property BEST confirms amyloid deposits in a tissue section?
- A Positive PAS staining with periodic acid
- B Metachromasia with crystal violet
- C Apple-green birefringence under polarized light after Congo red staining ✓
- D Positive Prussian blue staining
Correct answer: C. Apple-green birefringence under polarized light after Congo red staining
Explanation
Congo red staining followed by polarized light microscopy revealing apple-green (dichroic green) birefringence is the gold standard for amyloid identification. The characteristic appearance results from the beta-pleated sheet configuration of amyloid fibrils interacting with Congo red dye. Metachromasia with crystal violet and thioflavin-T fluorescence are also used but Congo red polarized microscopy is most specific and standard.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.