BACKGROUND: Neuroblastoma (NB) occurs rarely during adolescence, and information is scarce on its characteristics and clinical course in this age group. METHODS: Patients with NB who were included in the Italian Neuroblastoma Registry were considered for the current study. The clinical characteristics and survival of adolescents (age at diagnosis between 10 yrs and 18 yrs) were compared with those of children (ages 1-9 yrs). Infants (age < 1 yr) were excluded because of their well known favorable clinical course. RESULTS: Between 1116 children and 53 adolescents who were evaluated, no differences were documented with regard to the primary tumor site and the prevalence of advanced stage at diagnosis. If only patients with Stage IV NB were considered, then adolescents were less likely to be diagnosed with bone/bone marrow metastases (77%) compared with children (94%; P = 0.038), but adolescents were more likely to have metastases at unusual sites, such as the lung parenchyma or the central nervous system (23% vs. 7%, respectively; P = 0.005). With regard to biologic characteristics, adolescents did not differ significantly from children, although they always had a lower prevalence of unfavorable markers. In particular, MYCN amplification was documented in 21% of children and in 11% of adolescents (P = 0.173). At age 10 years, adolescents had a 20% overall survival rate and a 22% event-free survival rate. Adolescents who had resectable disease had a 73% overall survival rate, which was worse compared with the rate among children with the same disease stage (89%), although the difference did not reach statistical significance (P = 0.159). No differences in survival were observed among patients with Stage IV NB, and adolescents had a probability of survival almost identical to that among children (6% vs. 16%, respectively; P = 0.481). However, when the analysis was restricted to events that occurred after patients developed a recurrence, even if the final outcome was poor for both groups, the difference was statistically significant (P = 0.022) mostly because of the more indolent disease course observed among the adolescents. This effect was even more evident for patients with Stage IV NB. When the 6-year cut-off point was used to separate children from adolescents, a significantly worse overall survival rate (P = 0.036) was documented for adolescents who had resectable disease (81% vs. 93% in children). CONCLUSIONS: NB in adolescents had clinical and biologic characteristics similar to those observed among children. The clinical course of NB probably is correlated significantly with age at diagnosis, but information is scarce on the role of the biologic risk factors in this age group. The authors were able to identify a group of patients with a cut-off age between 6 years and 10 years that had a more indolent course but a worse prognosis.