Histological, histochemical, and ultrastructural features of mitochondrial DNA-related cardiomyopathy. (A) Histological examination of explanted left ventricular tissue from a patient with a homoplasmicmt-tRNAIle mutation reveals enlarged cardiomyocytes with prominent cytoplasmic vacuolization (H&E, 20×). (B) Vacuolescontain lipid droplets that stain with Oil Red O (40×). (C) Sequential cytochrome c oxidase/succinate dehydrogenase histochemistry shows several cytochrome c oxidase-deficient cardiomyocytes (blue) with scattered cytochrome c oxidase-positive cells (brown, 40×). (D) Ultrastructural analysis reveals proliferation of polymorphic mitochondria and displacement of sarcomeres (uracylacetate lead citrate, 3150×). Cardiac involvement in mitochondrial DNA disease: clinical spectrum, diagnosis, and management: Bates MG, Bourke JP, Giordano C, d'Amati G, Turnbull DM, Taylor RW - European heart journal (2012). Not altered. CC.