Fine-needle aspiration of abdominal fat pad for amyloid detection: a clinically useful test?

Fine-needle aspiration of abdominal fat pad (FNAFP) is commonly employed for the diagnosis of systemic amyloidosis, a disease with highly variable clinical manifestations, often presenting difficult patient management problems. We evaluated the role of FNAFP particularly in reference to its clinical usefulness. Pathology reports and clinical histories of 91 consecutive cases of FNAFP with Congo red (CR) staining at The Johns Hopkins Hospital (1999-2000) were reviewed. Major emphases were assessment of the clinical utility of the test, correlation with concurrent or subsequent biopsies, and treatment strategies. The primary indications for FNAFP were monoclonal gammopathy (34%), cardiomyopathy (22%), renal insufficiency (20%), neuropathy (8%), plasma cell dyscrasia (6%), and other conditions (10%). Of the 91 patients who underwent FNAFP, the results were as follows; 20 cases (22%) positive; 62 cases (68%) negative; eight cases (9%) insufficient for diagnosis; and one case (1%) equivocal. Of the 20 positive cases, follow-up biopsies were performed on 11 cases, of which six were positive and five were negative for amyloid by CR. Of the 62 negative cases, follow-up biopsies were performed on 19 cases, 14 of which were negative and five positive for amyloid by CR. A follow-up biopsy on the single equivocal case was positive for amyloid by CR. Twenty-one patients positive for amyloid, based on initial or follow-up biopsies, were managed symptomatically without any specific treatment for amyloidosis. One patient, who was specifically treated for amyloidosis by melphalan and dexamethasone, died 1 wk after therapy. Three patients with multiple myeloma and amyloidosis underwent chemotherapy. We conclude that primary clinical indications for FNAFP for amyloidosis are highly variable. An FNAFP result is often not considered clinically conclusive and is followed by further invasive procedures to detect amyloid (55% of our positive and 31% of our negative FNAFP cases were rebiopsied). The estimated sensitivity and specificity of FNAFP were 75% and 92%, respectively. Overall, the reliance on the results of FNAFP depended on the degree of clinical suspicion of the treating physician. Although in the majority of cases diagnosis of amyloidosis did not alter the treatment strategies, a conclusive positive result helped in ruling out other underlying conditions as the cause of patients' symptoms.