CONVENTIONAL VERSUS MODIFIED MORPHOLOGIC CRITERIA FOR GANGLIONEUROBLASTOMA - A REVIEW OF CASES FROM THE PEDIATRIC-ONCOLOGY-GROUP

Background.-Conventional criteria for ganglioneuroblastoma (GNB) do no t require the presence of ganglioneuromatous component for pathologic diagnosis. This leads to inclusion of a mixed variety of neuroblastic tumors in the category of GNB. Therefore, GNB diagnosed by conventiona l criteria includes tumors showing more than 5% ganglion cells but no predominant ganglioneuromatous component, as well as tumors containing predominant ganglioneuromatous component. By previously described mod ified criteria, the former would be considered differentiating neurobl astoma (NB), and only the latter would be considered GNB. Data on Pedi atric Oncology Group cases were analyzed to compare the prognostic sub groups of GNB diagnosed by conventional and modified criteria. The two prognostic subgroups (low risk and high risk) were defined on the bas is of previously described prognostic differences between histologic g rades of differentiating NBs and subtypes of GNB. Methods.-Pathologic data from cases of neuroblastic tumors registered on Pediatric Oncolog y Group NE protocols 8104 and 8441 were reviewed. The GNBs diagnosed b y conventional and modified criteria were divided into low-risk and hi gh-risk histology subgroups as follows: (1) GNB by conventional criter ia: low-risk group, differentiating NE of histologic grades 1 and 2 an d GNB of intermixed and borderline subtypes; high-risk group, differen tiating NE of histologic grade 3 and GNB of nodular subtype; (2) GNB b y modified criteria: low-risk group, GNB of intermixed and borderline subtypes; high-risk group, GNB of nodular subtype. Results.-The low- a nd high-risk subgroups of GNBs diagnosed by conventional (69 cases) an d modified (36 cases) criteria showed statistically significant differ ences in survival (P = .03 and .01, respectively). However, from the h istologic point of view, GNBs diagnosed by modified criteria form a mo re uniform morphologic group, which can be divided into low- and high- risk subgroups by a single set of morphologic criteria. In contrast, G NBs diagnosed by conventional criteria form a heterogeneous group, whi ch requires two sets of criteria (ie, histologic grade and subtypes of GNB) for its classification into low- and highrisk subgroups. Conclus ions.-The modified criteria for GNB define a morphologically uniform g roup of neuroblastic tumors to which a single set of prognostic criter ia can be applied. It is recommended that the term GNB should be used both clinically and pathologically to designate a distinctive subgroup of neuroblastic tumors, in contrast to the current use, which designa tes both NB and GNB.