Exploring the usefulness of prostate tissue in diagnosing transthyretin amyloidosis and predicting cardiac outcomes: an autopsy-based study

This study aimed to evaluate the clinicopathological features of prostatic transthyretin-derived amyloid (ATTR) deposition in patients with sporadic cardiac ATTR amyloidosis (sATTR-CA), investigate the correlation between the severity of amyloid deposition in the prostate and heart, and identify prostatic deposition patterns that could predict severe cardiac involvement. We evaluated 35 male autopsy cases with sATTR-CA. The severity of prostatic and cardiac ATTR deposition was assessed semiquantitatively. Using digital pathology, we quantitatively evaluated the immunohistochemical deposition burden of ATTR in the prostatic interstitium and myocardium. Amyloid deposition was detected in 18 cases (51%) in haematoxylin and eosin (H&E)-stained specimens, and ATTR deposition was confirmed in 29 cases (83%) using Congo red staining and immunohistochemistry for transthyretin. The group with identifiable amyloid deposition in the prostate on H&E staining had significantly more severe ATTR deposition in the heart than the group without prostatic deposition. The severity of deposition at all prostatic sites correlated positively with semiquantitative and quantitative deposition severity scores in the heart. Notably, the severity of deposition in the prostatic intraglandular interstitium and extraglandular vessels showed a strong positive correlation with the severity of sATTR-CA. Prostatic ATTR deposition was prevalent and may be a useful organ for diagnosing ATTR deposition. Additionally, the severity of prostatic deposition correlated with the severity of cardiac deposition. As biopsy materials often lack extraglandular tissue, it is crucial not to overlook intraglandular interstitium deposits on H&E staining.