Neuroblastoma Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Cellular Classification of Neuroblastic Tumors
Neuroblastomas are classified as one of the small, round, blue cell tumors of childhood. They are a heterogenous group of tumors composed of cellular aggregates with different degrees of differentiation, from mature ganglioneuromas to less mature ganglioneuroblastomas to immature neuroblastomas, reflecting the varying malignant potential of these tumors.
There are two cellular classification systems for neuroblastoma.
- International Neuroblastoma Pathology Classification (INPC) System: The INPC system involves evaluation of tumor specimens obtained before therapy for the following morphologic features:[2,3,4,5]
- Amount of Schwannian stroma.
- Degree of neuroblastic maturation.
- Mitosis-karyorrhexis index of the neuroblastic cells.
Favorable and unfavorable prognoses are defined on the basis of these histologic parameters and patient age. The prognostic significance of this classification system, and of related systems using similar criteria, has been confirmed in several studies.[2,3,4]
In the future, the INPC system is likely to be replaced by a system that does not include patient age as a part of cellular classification.
Table 1. Prognostic Evaluation of Neuroblastic Tumors According to the International Neuroblastoma Pathology Classification (Shimada System)a
|International Neuroblastoma Pathology classification||Original Shimada classification||Prognostic group|
|MKI: mitosis-karyorrhexis index.|
|a Reprinted with permission. Copyright © 1999 American Cancer Society. All rights reserved.Hiroyuki Shimada, Inge M. Ambros, Louis P. Dehner, Jun-ichi Hata, Vijay V. Joshi, Borghild Roald, Daniel O. Stram, Robert B. Gerbing, John N. Lukens, Katherine K. Matthay, Robert P. Castleberry, The International Neuroblastoma Pathology Classification (the Shimada System), Cancer, volume 86, issue 2, pages 364-72.|
|b Subtypes of neuroblastoma were described in detail elsewhere.|
|c Rare subtype, especially diagnosed in this age group. Further investigation and analysis required.|
|d Prognostic grouping for these tumor categories is not related to patient age.|
|<1.5 yrs||Poorly differentiated or differentiating & low or intermediate MKI tumor|
|1.5-5 yrs||Differentiating & low MKI tumor|
|<1.5 yrs||a) undifferentiated tumorc|
|b) high MKI tumor|
|1.5-5 yrs||a) undifferentiated or poorly differentiated tumor|
|b) intermediate or high MKI tumor|
|≥5 yrs||All tumors|
|Ganglioneuroblastoma, intermixed||(Schwannian stroma-rich)||Stroma-rich Intermixed (favorable)||Favorabled|
|Maturing||Well differentiated (favorable)||Favorabled|
|Ganglioneuroblastoma, nodular||(composite Schwannian stroma-rich/stroma-dominate and stroma-poor)||Stroma-rich nodular (unfavorable)||Unfavorabled|
Most neuroblastomas with MYCN amplification in the INPC system also have unfavorable histology, but about 7% have favorable histology. Of those with MYCN amplification and favorable histology, most do not express MYCN, despite the gene being amplified, and have a more favorable prognosis than those who do express MYCN.
- International Neuroblastoma Risk Group (INRG) Classification System: The INRG used a decision-tree analysis to compare 35 prognostic factors in more than 8,000 patients with neuroblastoma from a variety of clinical trials. The following INPC (Shimada system) histologic factors were included in the analysis:[8,9]
- Diagnostic category.
- Grade of differentiation.
- Mitosis/karyorrhexis index.
Because patient age is used in all risk stratification systems, a cellular classification system that did not employ patient age was desirable, and underlying histologic criteria, rather than INPC or Shimada Classification, was used in the final decision tree. Histologic findings discriminated prognostic groups most clearly in two subsets of patients, as shown in Table 2.