Incidental Atrial Amyloid on Surgical Pathology Revealing Transthyretin Cardiac Amyloidosis.

BACKGROUND: Atrial amyloid is frequently encountered incidentally on surgical specimens and often attributed to isolated atrial amyloidosis. However, atrial amyloid may also represent early transthyretin amyloid (ATTR) cardiac amyloidosis (CA), a treatable condition. CASE SUMMARY: A 70-year-old man presented with worsening dyspnea, lower-extremity edema, and atrial fibrillation. He underwent coronary artery bypass grafting with MAZE procedure and left atrial appendage ligation. Pathology of the atrial appendage revealed Congo red-positive amyloid deposits. Mass spectrometry confirmed transthyretin-type amyloid. Transthyretin gene sequencing was negative, and technetium-99m pyrophosphate scintigraphy demonstrated significant cardiac uptake, confirming wild-type ATTR CA. He was treated with tafamidis and spironolactone, maintained sinus rhythm after cardioversion, and remained clinically stable at 1-year follow-up. DISCUSSION: This case highlights the diagnostic value of atrial tissue histopathology in detecting occult ATTR amyloidosis. Further, it emphasizes the importance of comprehensive evaluation and early initiation of disease-modifying therapy. Proper evaluation of atrial amyloid can alter management and improve patient outcomes. TAKE-HOME MESSAGES: Atrial amyloid identified on surgical pathology should prompt comprehensive evaluation for CA. Atrial amyloid should not be assumed to represent isolated atrial amyloidosis, as it may provide an opportunity for early diagnosis and initiation of disease-modifying therapy.