Retroperitoneal ganglioneuroblastoma. Report of a case diagnosed by fine needle aspiration cytology and electron microscopy.

Fine needle aspiration performed on a large retroperitoneal mass in a 12-year-old boy showed neuroblasts in different stages of maturation intermingled with ganglion cells, leading to a cytologic diagnosis of ganglioneuroblastoma. This diagnosis was supported by electron microscopic study of the aspirate, which showed features of neuroblastic differentiation, and by histologic study of the resected tumor.