Ganglioneuromas, ganglioneuroblastomas, and neuroblastomas differ from one another in terms of the stage of neuroblast maturation. The ganglioneuromas, which are composed of mature ganglion cells, are considered benign tumors. Ganglioneuroblastomas are less mature forms. They are regarded as more aggressive tumors, and they generally develop in small children (mean age at onset: 2 years). They tend to produce catecholamines, in particular vanillylmandelic acid and homovanillic acids, which are important diagnostic markers. For patients with ganglioneuroblastomas, the prognosis is relatively good: these tumors may regress spontaneously or mature into ganglioneuromas. Regression occurs in 1–2% of all cases, and the causes are unknown ¹⁾.