Paraganglia mimicking metastatic seminomatous tumor.

Two cases are presented in which microscopic groups of retroperitoneal paraganglionic cells simulated metastatic seminomatous tumor. Both patients had histories of mixed testicular germ cell tumor with abdominal metastases and had been treated with chemotherapy. Persistent retroperitoneal disease was favored on follow-up imaging studies. Subsequent retroperitoneal lymph node dissection disclosed multifocal epithelioid cell groups with clear/vacuolated cytoplasm in the fibroconnective and adipose tissue, ranging from 1.0 to 3.0 mm in size. These cell groups were initially interpreted as recurrent metastatic seminoma, but were later reinterpreted as paraganglionic cells, which were confirmed by immunohistochemical analysis. The pathologic features for distinguishing paraganglionic cells from metastatic seminoma are discussed. Awareness of the presence of paraganglia and their distinction from metastatic disease is of practical importance in avoiding an overdiagnosis of malignancy and assuring proper patient management.