Frequency and extent of cytokeratin expression in Paraganglioma: an Immunohistochemical study of 60 cases from 5 anatomic sites and review of the literature

Summary The absence of cytokeratin expression in paraganglioma helps to differentiate it from other neuroendocrine neoplasms such as carcinoid tumor. Although rare cytokeratin positive paragangliomas have been reported, there are no large systematic studies of this phenomenon. The aim of this study was to determine the frequency and extent of cytokeratin expression in paragangliomas using a large cohort of cases from multiple anatomic sites. Immunohistochemical staining for keratin AE1/AE3 (mouse monoclonal, MAB3412; Millipore) and CAM 5.2 (mouse monoclonal, 349 205; Becton-Dickinson) was performed 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). Cytokeratin expression was identified in only 2/60 (3.3%) cases. One was a mediastinal paraganglioma with moderate to strong expression of keratin AE1/AE3 and CAM 5.2 in