Presumed drug toxicity. Biopsy of a graft in a patient, OT 74, who was deeply jaundiced at one year and five months after transplantation. The liver functions returned to normal after azathioprine was replaced with cyclophosphamide and after the prednisone dosage was lowered to less than half of its previous level. a, Centrilobular hepatocytes are swollen and show abnormal variation in nuclear size. Hematoxylin and eosin, ×200. b, Centrilobular cholestasis with bile thrombi in dilated canaliculi. Bile stain, ×200. c, Normal portal tract. Hematoxylin and eosin, ×200.