A comprehensive panel of testing for amyloidosis.

Abstract

Amyloidosis encompasses a spectrum of rare disorders characterized by extracellular amyloid deposition. Achieving an accurate early diagnosis of systemic amyloidosis necessitates biopsy-specific pathological evaluation. Formalin-fixed, paraffin-embedded liver biopsy specimens were examined using Congo red staining, electron microscopy, immunohistochemistry (IHC), immunofluorescence, and Congo red-assisted laser microdissection with mass spectrometry (LMD/MS). Failure Mode and Effects Analysis (FMEA) was employed for risk mitigation and quality control. Classical Congo red staining exhibited brick-red coloration, enhanced alkalinization, reduced permanganate staining, and characteristic apple-green birefringence under polarized light. Trypsin-digested IHC demonstrated kappa light chain positivity and lambda negativity, with improved background clarity compared to other retrieval methods-results concordant with electron microscopic colloidal gold staining, albeit with higher tissue consumption. Congo red-polarized microscopy permitted direct amyloid deposit localization. Subsequent LMD/MS identified immunoglobulin kappa light chain as the pathogenic precursor protein, though at increased expense. Congo red staining under polarized light remains the cornerstone technique for amyloid detection. LMD/MS provides superior specificity in amyloid typing relative to IHC, immunofluorescence, or electron microscopy, proving particularly advantageous for limited samples. Traditional methods remain valuable for validation when tissue is abundant. Histopathological assessment continues to be the diagnostic gold standard for hepatic amyloidosis; systematic integration and analytical refinement of these techniques are imperative for enhancing diagnostic accuracy.