High amyloid detection rate in abdominal wall liposuction biopsy for probable ATTR cardiac amyloidosis diagnosed by pyrophosphate scintigraphy

Background With the increasing prevalence of transthyretin cardiac amyloidosis (ATTR-CA) in an aging society, particularly in cases without genetic mutations, early diagnosis and treatment initiation are crucial for extending healthy life expectancy. The Japanese Clinical Guidelines for Cardiac Amyloidosis recommend pathological confirmation of transthyretin (TTR) amyloid deposition in myocardial or other tissues for a definitive diagnosis. Tissue diagnosis is also essential for initiating disease-specific treatments, such as TTR tetramer-stabilizing therapy in Japan. However, amyloid detection rates using less invasive techniques, such as abdominal wall liposuction or gastrointestinal biopsy, have been reported to be as low as 15–40%, particularly in wild-type (ATTRwt) cases. Consequently, most diagnoses still rely on invasive myocardial biopsy. Purpose This study aimed to evaluate the amyloid positivity detection rate in abdominal wall liposuction biopsy among patients with probable ATTR-CA. Methods We enrolled patients with probable ATTR-CA diagnosed by positive pyrophosphate scintigraphy and performed abdominal wall liposuction biopsy. The obtained specimens were analyzed using hematoxylin and eosin (H&E) and direct fast scarlet (DFS) staining. If DFS staining was positive, immunohistochemistry for TTR was performed to confirm ATTR deposition. Results A total of 20 consecutive patients with probable ATTR-CA were included (mean age: 80.7 ± 5.0 years; 19 males; 19 ATTRwt, 1 ATTR variant). Amyloid deposition was detected in 16 patients, all confirmed by TTR immunohistochemistry, yielding a positivity rate of 80%—substantially higher than the previously reported 15%. Conclusion We demonstrated a significantly higher amyloid detection rate in abdominal wall liposuction biopsy than previously reported. This technique enables definitive diagnosis of ATTR-CA less invasively, could substantially reduce patient burden, facilitate early treatment initiation, and improve clinical outcomes. We present these findings along with details of the biopsy procedure.