Work

Mass Spectrometry-Based Amyloid Typing in FFPE Biopsies: A Five-Year Prospective Experience from a Tertiary Academic Center in Spain

Year: 2026

Type: preprint

Abstract: Background Accurate amyloid subtyping is essential for patient management but remains challenging with antibody-based methods. We prospectively evaluated a standardized LC-MS/MS workflow for routine amyloid typing, focusing on diagnostic yield, operational performance, and added value in cases not fully resolved by conventional methods. Methods From 2020 to 2025, 115 FFPE biopsies from patients with suspected amyloidosis were analyzed at Hospital Universitario A Coruña, Spain, without laser microdissection. Proteins were identified and quantified using PEAKS, with a peak-area cutoff ≥10 5 for candidate fibril proteins. Results Seventy-nine cases (69%) were amyloid-positive, 22 (19%) negative and 14 (12%) indeterminate. AL (51%), ATTR (32%) and AA (10%) predominated, with additional AH (5%), mixed ATTR+AL, hereditary ATTRv and AIns amyloidoses. Binary concordance with conventional techniques ranged from 85.7% to 91.5%. LC-MS/MS provided additional diagnostic information in 64/110 evaluable cases (58.2%), including additional subtyping information in 53/110 (48.2%). The workflow also enabled relative quantification of variant versus wild-type TTR peptides and characterization of SAA post-translational modifications. Mean turnaround time was approximately two weeks and MS findings informed clinical management. Conclusions LC-MS/MS amyloid typing was clinically feasible in routine FFPE biopsies without laser microdissection and supported identification of common, rare and mixed amyloid types.

Source: medRxiv

DOI: 10.64898/2026.10.20.26364269