[The characteristics of mediastinal neuroblastoma and perspectives on surgical excision]

Thoracic (mediastinal) neuroblastomas (NB) have been reported to differ from abdominal (suprarenal and retroperitoneal) NB and to be associated with better prognosis. The comparison between them is rarely published. In this retrospective study, the characteristics of thoracic NB (17 cases) are investigated and compared with abdominal NB (51 cases). Regarding the diagnosis, thoracic NB presented in lower clinical stages I and II in 35.3% of cases, compared to 11.7% of abdominal NB in stages I and II (p<0.001). The disease was initially diagnosed at less than one year of age in 7/17 (41.2%) of thoracic NB and in 12/51 (23.5%) in abdominal cases (p<0.001). The median age at the time of initial diagnosis was 15.3 months for thoracic NB and 27.6 months for abdominal neuroblastoma (p<0.05). The cases with an elevated vanillylmandelic acid (VMA) and homovanyillic acid (HVA) excretion were 9/17 (52.9%) in the mediastinal NB, and 43/51 (84.3%) in the abdominal NB, respectively (p<0.05). The quantitative values of tumour markers were significantly lower in thoracic NB (0.85 vs. 2.14, p<0.001). Regarding surgery, complete tumour resection was achieved in 15/17 thoracic NB (88.2%) compared to 36/51 (70.6%) radicality in abdominal NB. Surgical complications developed in 5/17 thoracic procedures (29.4%) without a lethal outcome. The mean tumour mass of thoracic NB was 56.5 g vs. 106.3 g of abdominal neuroblastoma (p<0.001). The incidence of ganglioneuroblastoma in mediastinal tumours was 3/17 (17.6%) compared to 8/51 (15.7%) in abdominal NB (non significant). A favorable histology based on Shimada classification was found in 37% of the mediastinal neuroblastoma cases and in 22% in the abdominal NB cases (p<0.05). Regarding the biological properties, genetic malformations associated with NB were identified in 2 thoracic cases (1p deletion and polyploidy). Genetic changes were identified in 12 cases of abdominal NB (1p deletion in 4 cases, DNA ploidy in 6 cases, N-myc amplification in 1 case). One additional abdominal NB had 1p deletion, DNA ploidy and N-myc amplification. This study supports results of other investigations that thoracic NB differs significantly in many aspects from abdominal NB. Important differences in favorable histology and biological properties of thoracic NB have changed the concept of surgical treatment, although unnecessary attempts of surgical radicality still lead to serious complications. Complete excision remains the mainstay of therapy of localised thoracic NB, while in most abdominal tumours the aim of an initial operation should be sampling of tumour tissue for histology and molecular biological examination, with complete excision of the mass as the second priority.