The tertiary structure of amyloid protein consists of beta-pleated sheets. This is responsible for its affinity for Congo Red stain and the characteristic apple-green birefringence under polarized light (shown here). If the amorphous material in the lymph node is PAS+ and diastase-resistant and negative for Congo Red, it is most likely glycoprotein that may be seen with nodular lymphoma, Waldenstroms macroglobulinemia, immunoblastic lymphadenopathy, and various carcinomas. Image courtesy of : Ed Uthman, MD, Houston, Texas. Used with permission.