Implication of unfavorable histology, MYCN amplification and diploidy for stage I and II neuroblastomas

Surgery is the first line treatment for low-grade neuroblastomas. In stage I tumors, the presence of MYCN amplification is rarely detected and the Shimada histology is not always taken into consideration when deciding on the treatment. This study concerns the significance of these two factors in the evolution of children with low-grade neuroblastomas.

We analyzed the assessment and follow-up of children with low-grade neuroblastomas (stages I and II) with or without MYCN amplification, with either a favorable or unfavorable histology and with or without tumor cell diploidy. Favorable histology was defined as stroma-poor tumors with more than 5 % differentiating neuroblasts and a mitosis karyorrhexis index (MKI) of less than 100/5000 cells.

From 1995 to 2006, out of 114 neuroblastomas, nine (7.9 %) were stage I and 21 (18.4 %) stage II. Of these 30 patients, 27 underwent surgery alone and three received chemotherapy after surgery. The combination of MYCN amplification, unfavorable histology and diploidy was noted in one patient who developed metastases within two months. MYCN amplification alone was noted in two cases who are still tumor-free after two years. Unfavorable histology alone was noted in four patients, of whom one suffered a recurrence of the tumor (previously stage I) and three are tumor-free after six years. Tumor cell diploidy alone was present in 11 patients whose evolution is satisfactory.

Because MYCN amplification and unfavorable histology are rare in early stage neuroblastomas, these tumors may be misclassified if they are not investigated further. It seems that no single clinical or biological feature can be considered a significant factor in establishing a prognosis or determining whether additional treatment is required.