TNFRSF8 and Castleman disease: Congo red is a dye used for staining that selectively binds to β-folded proteins. In the diagnosis of Castleman disease, Congo red staining can help identify specific histological changes such as amyloidosis. In certain cases, additional markers such as CD10, CD30, EBER, IL-10, etc., can be used for specific identification (20, 25, 26).