Paraganglioma of the posterior mediastinum diagnosed by immunohistochemical staining.

Paraganglioma of the mediastinum are rare neoplasms. To date, no definitive morphologic criteria exist that correlate with the clinical outcome of these tumors. We have encountered a case of paraganglioma in which biological behavior was assessed by immunohistochemical staining to determine whether supplementary postoperative treatment was needed. A 28-year-old man came to our hospital because of an abnormal shadow on a radiogram of the chest. He had no symptoms. Hematological findings were unremarkable. Diagnostic imaging suggested a neurogenic tumor. Surgical resection was performed in September, 2002. A typical nesting pattern (Zellballen) and positivity for chromogranin on immunohistochemical staining were evident, indicating neuroendocrine characteristics, and paraganglioma was diagnosed. Tissue specimens indicated an MIB-1-labeling index of 1.3% on MIB-1 staining, and a relatively well maintained distribution of S-100 protein-positive sustentacular cells, which were suggestive of a benign tumor. The patient did not receive any supplementary therapy postoperatively but was given careful follow-ups.