Systematization of primary histopathologic and fine-needle aspiration cytologic features and description of unusual histopathologic features of neuroblastic tumors: a report from the Pediatric Oncology Group.

On the basis of a detailed review of the primary histopathologic features of 239 cases and the fine-needle aspiration cytologic features of seven cases, a systematized schema of differentiation, progressive maturation and organization, and biologic behavior in neuroblastic tumors (NTs) is presented. The differentiation is of the gangliocytic and schwannian lineages. Maturation occurs in differentiating neuroblasts, leading to the formation of various stages of ganglion cells and Schwann cells. Organization is characterized by nesting pattern, rosette formation, parallel arrangement of neuropil, and alignment of Schwann cells along the neurites. According to this schema the NTs can be arranged in the following order: undifferentiated, poorly differentiated, and differentiating neuroblastoma; nodular, intermixed, and borderline ganglioneuroblastoma; and ganglioneuroma. Formulation of such a schema is helpful in gaining a better understanding of the complex pathologic features and in defining the criteria for various types of NTs. Therefore, the schema also would be helpful in achieving uniformity and reproducibility of the diagnosis of various types of NTs. Previously unreported features related to shape, size, nucleus, and cytoplasm of neuroblasts; secondary changes and patterns; changes in the fibrovascular septa; and other morphologic aspects of NTs and features (such as large tumor cells, karyorrhectic cells in fine-needle aspiration biopsy, tumor giant cells, anaplasia, and nesting pattern of tumor cells that have not been sufficiently emphasized) also are described. The importance of these previously unreported and insufficiently emphasized features relates to the histologic and cytologic diagnosis of NTs. For example, some of the features, such as starry sky appearance and spindle-shaped neuroblasts, may be misleading if seen in a small biopsy specimen. Others, such as tumor giant cells resembling ganglion cells and nesting pattern, will provide clues to the correct diagnosis. Some of the features, such as sclerosing pattern, hyalinization, and dense lymphoplasmacytic infiltration, may be related to the phenomenon of regression exhibited by neuroblastomas.