Terminology and morphologic criteria of neuroblastic tumors - Recommendations by the International Neuroblastoma Pathology Committee

BACKGROUND, As part of the international cooperative effort to develop a co mplete set of International Neuroblastoma Risk Groups, the International Ne uroblastoma Pathology Committee (INPC) initialed activities in 1994 to devi se a morphologic classification of neuroblastic tumors (NTs; neuroblastoma, ganglioneuroblastoma, and ganglioneuroma). METHODS. Six member pathologists (H.S., I.M.A., L.P.D., J.H., V.VJ., and B. R.) discussed and defined morphologically based classifications (Shimada cl assification; risk group and modified risk group proposed by Joshi et al.) on the basis of a review of 227 cases, using various pathologic characteris tics of the NTs. The classification-grading system was evaluated for progno stic significance and biologic relevance. RESULTS. The INPC has adopted a prognostic system modeled on one proposed b y Shimada et al. It is an age-linked classification dependent on the differ entiation grade of the neuroblasts, their cellular turnover index, and the presence or absence of Schwannian stromal development. Based on morphologic criteria defined in this article, NTs were classified into four categories and their subtypes: 1) neuroblastoma (Schwannian stroma-poor), undifferent iated, poorly differentiated, and differentiating; 2) ganglioneuroblastoma, intermixed (Schwannian stroma-rich); 3) ganglioneuroma (Schwannian stroma- dominant), maturing and mature; and 4) ganglioneuroblastoma, nodular (compo site Schwannian stroma-rich/stroma-dominant and stroma-poor). Specific feat ures, such as the mitosis-karyorrhexis index, the mitotic rate, and calcifi cation, were also included to allow the prognostic significance of the clas sification to be tested. Recommendations are made regarding the surgical ma terials to use for an optimal pathobiologic assessment and the practical ha ndling of samples. CONCLUSIONS. The current article covers the essentials and important points regarding the histopathologic evaluation of NTs. Using the morphologic cri teria described herein, the INPC is proposing the International Neuroblasto ma Pathology Classification. It is reported in a companion article in this issue (Cancer 1999;86:363-71). Cancer 1999;86:349-63. (C) 1999 American Can cer Society.