Dermawan JK, et al. - Immunohistochemical staining for keratin AE1/AE3 and CAM 5.2 was done on whole-tissue sections from 60 resected paragangliomas from the head and neck (36), thorax (10), abdomen (8), intradural/epidural spine (5) and bone, left iliac (1) by the experts in order to discover the frequency and extent of cytokeratin expression in paragangliomas. In only 2/60 cases, cytokeratin expression was recognized. One was a mediastinal paraganglioma with modest to marked expression of keratin AE1/AE3 and CAM 5.2 in < 5% tumor cells. The other was a lumbar intradural paraganglioma positive for CAM 5.2 although negative for keratin AE1/AE3. For keratin AE1/AE3 and CAM 5.2, all other paragangliomas were negative. Thus, this study, which is the largest series of cytokeratin-stained whole-tissue sections of paragangliomas to date, validated the assertion that most paragangliomas are cytokeratin negative. Rare exceptions may be site-associated.