Figure 1c. Biopsy specimens from the tongue of a patient with known primary systemic amyloidosis and macroglossia. (a) Photomicrograph (hematoxylin-eosin stain) shows that the intrinsic musculature of the tongue is infiltrated by collagen-type extracellular material that stains pink. (b) Photomicrograph (Congo red stain) shows that the same areas as in a have strong affinity for the stain. (c) Photomicrograph obtained with polarized light microscopy of the same specimen as in b shows apple-green birefringence (arrow), which is diagnostic of amyloid.