Malignant paraganglioma of the organ of Zuckerkandl. Initially diagnosed as renal cell carcinoma by biopsy of a right humeral fracture lesion.

Malignant paraganglioma of the organ of Zuckerkandl (malignant POZ) in a 38-year-old woman is reported. Ten months before her death, the patient suffered from right shoulder pain. By biopsy of a pathological right humeral fracture, a histological diagnosis of metastatic renal cell carcinoma was initially made. However, autopsy revealed a left retroperitoneal tumor, which was diagnosed as malignant POZ. Upon immunohistochemical examination, tumor cells showed definite positivity for neuronspecific enolase (NSE) and chromogranins, and neurosecretory granules were found electron microscopically. The skeletal system is the most common site for distant metastases of malignant POZ. We were unable to find any previous reports of malignant POZ which were first manifested as humeral metastases, as in the present case. As paraganglioma might be histologically confused with a large variety of neoplasms (e.g. renal cell carcinoma), differential diagnosis of this condition is discussed.