Cytokeratin expression in adrenal phaeochromocytomas and extra-adrenal paragangliomas.

AIM To examine whether adrenal phaeochromocytomas and extra-adrenal paragangliomas are immunoreactive for commercially available and routinely used cytokeratin antibodies. METHODS 18 extra-adrenal paragangliomas and seven adrenal phaeochromocytomas were stained with CAM 5.2, AE1/3, and 34 beta E12 following microwave antigen retrieval of formalin fixed tissue. RESULTS A single case from the cauda equina was positive for both CAM 5.2 and AE1/3. In addition, two other cases--an intravagal and an orbital paraganglioma--also showed strong immunopositivity with CAM 5.2 and AE1/3. All phaeochromocytomas were negative with all epithelial markers. CONCLUSIONS Cauda equina paragangliomas are known to stain with cytokeratins; however, occasional paragangliomas from other sites may also be immunoreactive with cytokeratins. If the results of immunohistochemistry are not interpreted in the clinical and morphological context, the failure to recognise that extra-adrenal paragangliomas may on occasion react with anticytokeratin antibodies may lead to their being confused with metastatic carcinomas.