BACKGROUND: Congo red staining of fat pad fine needle aspiration specimens is a method utilized for evaluation of amyloid deposition. However, these specimens can pose diagnostic challenges for cytopathologists. As part of ongoing internal quality improvement measures, the objective of this study was to evaluate the intradepartmental interobserver agreement of these specimens and to identify factors that affect the variability of the interpretations.
METHODS: There were 7 participants, which included 3 trainees, 3 cytopathologists, and 1 cytotechnologist. Each participant reviewed 50 Congo red stained fat pad fine needle aspiration slides. The interpretations were categorized into 3 groups: negative, indeterminate/suspicious, and positive. The participants also noted any interpretation challenges they encountered for each case.
RESULTS: There was only slight interobserver agreement among all participants (κ = 0.133). Stratified by participant group, the interobserver agreement among the trainees was slight bordering on poor (κ = 0.028) and among cytopathologists was fair (κ = 0.249). The highest agreement between 2 observers was between 2 cytopathologists and the level of agreement was moderate bordering on fair (κ = 0.426). There were only 3 cases (6.0%) with full agreement among observers, while in 25 cases (50.0%), there were 2 category differences in interpretations. The primary diagnostic challenge reported by participants was when weak or focal birefringence was encountered as well as cases complicated by poor stain quality and overstaining.
CONCLUSIONS: We found only slight interobserver agreement among all study participants. A major area of challenge was cases with weak birefringence resulting in high variance of interpretation among participants.

BACKGROUND: Fine-needle aspiration (FNA) of abdominal fibroadipose tissue is a commonly utilized method for the detection of amyloidosis. While generally regarded as an accurate and specific detection method, the sensitivity is variable. The objective of this study was to investigate the performance of fat pad FNAs in detecting amyloidosis relative to other tissue biopsies.
METHODS: Fat pad FNA results from January 1, 2014, to December 31, 2022, were catalogued. Clinical data including FNA indication were ascertained for each case. The results of any subsequent tissue biopsy/biopsies evaluated for amyloidosis by Congo red staining were also assessed. Challenges to diagnostic interpretation were explored.
RESULTS: A total of 334 fat pad FNAs were identified. The most common indications were peripheral neuropathy (29.3%), cardiomyopathy/heart failure (28.1%), monoclonal gammopathy (27.8%), and multiple myeloma/lymphoplasmacytic lymphoma (21.0%). Cytologic interpretations were: 7 (2.1%) nondiagnostic, 284 (85.0%) negative, 18 (5.4%) indeterminate, 16 (4.8%) suspicious, and 9 (2.7%) positive for amyloid deposition. In our sample, 103 (30.8%) patients had Congo red testing performed on a subsequent surgical specimen(s) including: 3 of 7 of nondiagnostic cases, none which were positive on the subsequent surgical; 70 of 284 negative cases, 27 which were positive on the subsequent surgical; 11 of 18 indeterminate cases, 7 which were positive on the subsequent surgical; 13 of 16 suspicious cases, 2 which were positive on the subsequent surgical; and 6 of 9 positive cases, 3 which were positive on the subsequent surgical. Challenges to FNA interpretation included scant cellularity, focal staining/birefringence, and overstaining.
CONCLUSIONS: It is best to view fat pad aspiration versus other tissue biopsy results as complimentary diagnostic tests that should be interpreted in the context of the clinical setting and overall clinical suspicion for amyloidosis.

The anterior abdominal fat pad is associated with the falciform ligament in the upper middle/right abdomen and is frequently seen there in diagnostic imaging. It varies greatly in size and has often been described as an incidental finding in adults and has hitherto rarely been regarded as being illness-relevant. The aim of this study has been to assess whether the dimension of the corpus adiposum may be associated with body mass index. Ultrasound findings of 26 patients from birth until adolescence were analyzed for this purpose. In addition, an example from a recent dissection course has been included. The structure is constantly found with its smallest dimension in newborns, with a slight increase in infancy. The average dimensions were 7.6 by 3.5 by 0.7cm. The cubic volume correlated with age, weight and body mass index, whereas the latter association was strongest. Our data suggest that routinely determined dimension of falciform fat may be a surrogate parameter of relative body weight in childhood.

Fine-needle aspiration biopsy of the abdominal fat pad is considered to be a minimally invasive procedure for diagnosing systemic amyloidosis. However, this procedure is sometimes difficult and can be dangerous for elderly patients whose abdominal fat layer is thin because of malnutrition. In such cases, alternative diagnostic methods are required. We report three elderly patients with heart failure complicated by malnutrition. In all cases, electrocardiogram showed low voltage in the limb leads and a pseudoinfarct pattern in the chest leads, and echocardiography showed left ventricular wall thickening with granular sparkling appearance. These patients were suspected of having amyloid cardiomyopathy but could not undergo myocardial biopsies because of their poor conditions. After failed attempts at biopsy of the abdominal fat pad or the other organs, subcutaneous fat tissue biopsy over the hip led to the diagnosis of systemic amyloidosis with cardiomyopathy. The resultant diagnosis guided us to choose the appropriate treatment for the patients. This article illustrates that subcutaneous fat tissue biopsy of the hip could be a useful procedure for diagnosing systemic amyloidosis in elderly patients, particularly when a fat tissue biopsy of the abdomen is associated with a high risk of complications because of malnutrition.