Special Articles

1. Pathology of peripheral neuroblastic tumors−Favorable histology and unfavorable histology groups−

Atsuko Nakagawa
Division of Pathology, Department of Clinical Laboratory Medicine, National Center for Child Health and Development

Abstract

　　Peripheral neuroblastic tumors (neuroblastoma ; NBL, ganglioneuroblastoma ; GNB, ganglioneuroma ; GN) are embryonal tumors derived from neural crest cells and now considered as biologically heterogeneous. The unique clinical/biological behavior, such as spontaneous regression, tumor maturation, and aggressive progression, are closely related to the molecular properties of the individual tumors. Since the histologic features are phenotypical manifestations of various molecular alterations, the International Neuroblastoma Pathology Classification distinguishes them into a biologically favorable histology group (FH) and an unfavorable histology group (UH). The FH tumors fall within a conceptual framework of age-appropriate maturational sequence from poorly differentiated NBL (<18 months of age at diagnosis) to differentiating NBL (<60 months of age at diagnosis) to GNB intermixed subtype to GN. The FH tumors have favorable molecular backgrounds (non-amplified MYCN, high Trk A expression, near triploid chromosome). The UH tumors do not have a potential of age-appropriate maturation and consist of MYCN amplified tumors and MYCN non-amplified tumors. Characteristic histologic features of MYCN amplification include no sign of neuroblastic differentiation and increased mitotic and karyorrhectic activities, i.e. high MKI. In UH tumors, without MYCN amplification, their poor prognosis can be recognized only by pathology classification because the molecular alterations responsible for their clinical behavior are still unclear. The GNB nodular subtype is also divided into FH and UH according to the histologic evaluation used for the neuroblastomatous component.

Keywords：Neuroblastoma, International Neuroblastoma Pathology Classification, MYCN amplification