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Updated: Nov 21, 2025
Performing and Processing FNA of Anterior Fat Pad for Amyloid
Published on: October 30, 2010
Diagnostic value of electron microscopy detection using abdominal fat pad biopsy in systemic amyloidosis
Objective:
Electron microscopy (EM) was used to observe the deposition and ultrastructural characteristics of amyloids in abdominal adipose tissue, which provided a reliable basis for pathological diagnosis of systemic amyloidosis.
Materials And Methods:
42 patients with established amyloidosis and 8 controls underwent surgical biopsy of subcutaneous abdominal fat. The fat tissues were submitted concurrently in 4% buffered neutral formalin for histological sections preparation, in glutaraldehyde fixative for EM studies, and in saline solutions for immunofluorescence tests.
Results:
Light microscopy revealed marked brick-red staining in 11 of 42 samples, 6 moderate and 11 slight staining in the septum of cells, medium and small sized vessel, and apple green double refraction under polarized light microscopy. There were no significant differences in fat biopsies between the systemic amyloidosis and normal subjects in 14 cases. The EM showed approximate 10-nm-thick straight filaments in adipose tissue in all 42 cases with amyloidosis. The positive rate of diagnosis was 100%. Congo red stained sections alone in cases with scant amyloid led to false negative results, but the EM was able to characterize the amyloid protein in all cases.
Conclusion:
Therefore, preliminary diagnosis of suspected cases can be made by Congo red staining, but the final diagnosis requires an electron microscopic examination.
Insights
Electron microscopy (EM) of abdominal fat biopsies reliably diagnoses systemic amyloidosis by identifying characteristic amyloid filaments. While Congo red staining offers preliminary results, EM provides definitive pathological diagnosis.
Area of Science:
- Pathology
- Electron Microscopy
- Systemic Amyloidosis
Background:
- Systemic amyloidosis diagnosis can be challenging.
- Abdominal adipose tissue is a potential biopsy site.
Purpose of the Study:
- To evaluate electron microscopy (EM) for diagnosing systemic amyloidosis using abdominal fat biopsies.
- To compare EM findings with traditional Congo red staining.
Main Methods:
- Surgical biopsies of subcutaneous abdominal fat were obtained from 42 patients with amyloidosis and 8 controls.
- Tissues were prepared for light microscopy, EM, and immunofluorescence.
- EM utilized glutaraldehyde fixation for ultrastructural analysis.
Main Results:
- Light microscopy with Congo red staining showed variable results, with some false negatives.
- Electron microscopy detected characteristic ~10-nm-thick amyloid filaments in all 42 amyloidosis cases (100% diagnostic rate).
- EM successfully characterized amyloid protein even when Congo red staining was insufficient.
Conclusions:
- Congo red staining can provide a preliminary diagnosis of suspected amyloidosis.
- Electron microscopy is essential for definitive pathological diagnosis of systemic amyloidosis.
- Abdominal fat biopsy analyzed by EM offers a reliable diagnostic method.
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