Diagnostic Utility of Trichrome Stain for the Evaluation of Amyloid Deposition in Tissue Sections
J Karamchandani, JD Faix, G Berry, A Sangoi. Stanford University Medical Center, Stanford, CA
Background: Amyloid is customarily identified by apple-green birefringence under polarized light, though the use of Congo red staining for amyloid detection in routine surgical pathology can be fraught with difficulty as the degree of alcohol differentiation can affect sensitivity. In an informal setting, we have characterized a unique pattern of amyloid staining when viewed with trichrome stain. Given this finding, a formal comparison of the amyloid staining properties of Congo red and trichrome was performed, results which have not previously been reported.
Design: Trichrome and Congo red stains were performed on formalin-fixed paraffin embedded blocks from 10 cases. Trichrome stains employed DAKO's Gomori's Trichrome Kit with an Artisan automated slide stainer. Where possible, thioflavin S staining or electron microscopy was performed to further confirm amyloid deposition. Staining intensity was semiquantitatively scored as 0 to 3.
Results: Amyloid appears grayish-blue on trichrome stained section by light microscopy (LM), and has a consistently distinct appearance from that of collagen (dark blue). The presence of amyloid was further established with either Thioflavin S (viewed with UV light) or electron microscopy. In 5/10 cases, trichrome stain suggested greater presence of amyloid than Congo red. Staining intensity by organ is listed in Table 1.
Table 1EM=electron microscopy, T-S=thioflavin S, N/A=not available
|Organ||Diagnosis||Trichrome (LM)||Congo Red (polarized)||Additional Studies|
|Prostate||Seminal vesicle amyloidosis||3||3||N/A|
|Soft tissue (abdomen)||Amyloidosis||3||3||T-S|
Conclusions: While Thioflavin S staining examined under UV light and/or ultrastructural analysis are highly sensitive and specific for amyloid detection, Congo red stain is routinely employed in surgical pathology to detect amyloid. Congo red requires procedural proficiency for reliable diagnostic utility, as nonspecific and false negative staining can occur. Trichrome's unique tinctorial staining pattern may highlight more amyloid than is detected with routine Congo red staining when viewed with polarization. Trichrome's low procedural complexity, tinctorial reproducibility, and use with LM further advocate its use as an adjunct stain for diagnostic amyloid detection.
Monday, March 9, 2009 9:30 AM
Poster Session I Stowell-Orbison/Autopsy Award # 245, Monday Morning