Performing and Processing FNA of Anterior Fat Pad for Amyloid

Abstract

Historically, heart, liver, and kidney biopsies were performed to demonstrate amyloid deposits in amyloidosis. Since the clinical presentation of this disease is so variable and non-specific, the associated risks of these biopsies are too great for the diagnostic yield. Other sites that have a lower biopsy risk, such as skin or gingival, are also relatively invasive and expensive. In addition, these biopsies may not always have sufficient amyloid deposits to establish a diagnosis. Fat pad aspiration has demonstrated good clinical correlation with low cost and minimal morbidity. However, there are no standardized protocols for performing this procedure or processing the aspirated specimen, which leads to variable and nonreproducible results. The most frequently utilized modality for detecting amyloid in tissue is an apple-green birefringence on Congo red stained sections using a polarizing microscope. This technique requires cell block preparation of aspirated material. Unfortunately, patients presenting in early stage of amyloidosis have minimal amounts of amyloid which greatly reduces the sensitivity of Congo red stained cell block sections of fat pad aspirates. Therefore, ultrastructural evaluation of fat pad aspirates by electron microscopy should be utilized, given its increased sensitivity for amyloid detection. This article demonstrates a simple and reproducible procedure for performing anterior fat pad aspiration for the detection of amyloid utilizing both Congo red staining of cell block sections and electron microscopy for ultrastructural identification.

Detection of amyloid in abdominal fat pad aspirates in early amyloidosis: Role of electron microscopy and Congo red stained cell block sections

“…[20] In 24 cases, representative fibroadipose tissue was submitted concurrently in 10% formalin for cell block preparation and in glutaraldehyde fixative for EM studies. EM was not performed in 9 cases by some cytopathologists.…”

Immunoglobulin Light-Chain Amyloidosis: From Basics to New Developments in Diagnosis, Prognosis and Therapy

“…These two procedures are easily performed, carry little risk to the patient and have a combined diagnostic sensitivity of 85% [35,36], making them an excellent initial option for pathological confirmation. A video on the fat pad aspiration procedure is available [37]. For the remaining 15% of patients negative for amyloid in SFA and bone marrow biopsy, a thorough reexamination of 3 slides by two experienced pathologists has been shown to increase sensitivity [38] and could be considered.…”

Abdominal subcutaneous fat pad aspiration and bone marrow examination for the diagnosis of AL amyloidosis: the reliability of immunohistochemistry

“…Cell block preparations of fat pad aspiration material were made by a previously reported method [14]. Serial sections were stained with hematoxylin and eosin, periodic acid-Schiff, and Congo red stain.…”