Potential thioflavin T false positives in lipomembranous changes in adipocytes during systemic amyloidosis diagnosis

The diagnosis of systemic amyloidosis relies on the detection of amyloid deposition in the tissue, often utilizing biopsy specimens from the abdominal skin owing to their minimal invasiveness. Several amyloid staining methods, including Congo Red, Direct Fast Scarlet (DFS), and Thioflavin T (ThT), have been employed for visualization. Lipomembranous fat necrosis (LFN) is a non-specific reaction pattern of adipose tissue to injury, typically derived from blood insufficiency across a wide range of clinical conditions or diseases. It is characterized by the presence of eosinophilic, crenulated, and/or serpiginous membranes in fat lobules. We encountered a patient in whom ThT yielded suspiciously positive results in amyloidosis screening tests. Furthermore, our retrospective observations suggested that ThT staining was positive for LFN, whereas DFS and Congo red staining yielded negative results. The awareness that LFN can result in false-positive ThT staining during amyloid screening is crucial to avoiding the misdiagnosis of systemic amyloidosis. Furthermore, skin samples should not be collected from areas prone to developing lipomembranous changes. The use of more than two different stains for skin biopsy specimens is recommended.