Differential diagnosis and unusual diffuse cytokeratin expression in renal paraganglioma: A case report.

Paraganglioma is a rare neuroendocrine tumor arising from undifferentiated cells of the primitive neural crest. We report a case of renal paraganglioma in a 67-year-old patient. Computed tomography demonstrated a solid mass in the middle and lower pole of the right kidney. Sonography revealed an enlarged right kidney with an irregular shape but distinct border. Renal cell carcinoma was diagnosed provisionally; the tumor was completely resected and submitted for pathological examination. Unexpectedly, histopathology and immunohistochemistry confirmed paraganglioma arising from the renal parenchyma. In this study, we report the exceptional occurrence of Paired box gene 8 (PAX-8) expression in a renal paraganglioma. In addition, we demonstrated diffuse cytokeratin positivity in this renal paraganglioma. Although our report of a paraganglioma originating from the kidney is not unique, our finding expands the known immunophenotypic spectrum of this tumor. The awareness of the possible occurrence of cytokeratin diffuse positivity in paraganglioma is relevant to avoiding misdiagnosis of paraganglioma.