Congo red stain
Pronunciation: KONG-go red stayn
Histochemical stain that produces apple-green birefringence under polarized light when binding to amyloid deposits in cardiac tissue.
Full Definition
Congo red stain is the gold standard histochemical technique for identifying amyloid deposits in cardiac pathology. When applied to tissue sections containing amyloid proteins, this stain produces a characteristic orange-red color under ordinary light microscopy. However, the pathognomonic feature is the apple-green birefringence observed when the same sections are examined under polarized light. This unique optical property is specific for amyloid and helps differentiate it from other protein deposits. In cardiac amyloidosis, Congo red staining reveals amyloid deposition in vessel walls, interstitium, and around myocytes, which is crucial for diagnosis and typing of the amyloid protein involved.
Usage
Usage note: Always mention both the orange-red color and apple-green birefringence when describing positive Congo red results.
In Context
- "Congo red stain demonstrated apple-green birefringence in the myocardial vessel walls, confirming amyloid deposition." — Histopathology report
- "The diagnosis of cardiac amyloidosis was established by positive Congo red staining with characteristic polarization properties." — Cardiac biopsy analysis