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Neuroblastoma

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3. Histologic Evaluation of
Neuroblastoma

  • PNT comprises two histologic cell types.
    1. Neuroblastic tumor cells
    2. Schwann cells and Schwannian stroma – induced by the neuroblastic cells during differentiation
  • Divided into histologic subtypes depending on the degrees of:
    1. Differentiation and maturation of neuroblastic cells (tumor cells)
    2. Schwann cells/Schwannian stroma

International Neuroblastoma Pathology Classification (INPC) of Peripheral Neuroblastic Tumors

  • Histologic evaluation of PNT Based on “International Neuroblastoma Pathology Classification (INPC)”
    1. Neuroblastoma (NB) – Schwannian stroma-poor
      • Undifferentiated NB
      • Poorly differentiated NB
      • Differentiating NB
    2. Ganglioneuroblastoma (GNB) – Schwannian stroma-rich
      • Intermixed GNB
      • Nodular GNB
    3. Ganglioneuroma (GN) – Schwannian stroma-dominant
      • Maturing GN
      • Mature GN
Summary of PNT differentiation – used for INPC

1. Neuroblastoma (NB) Subtype

  • Neuroblastoma (NB, Schwannian stroma-poor form, <50% of the tumor volume
  • Further divided into three groups based on the degrees of neuroblastic cell differentiation.
    1. Undifferentiated NB (UD-NB)
      • Undifferentiated small round blue neuroblastic cells
      • No neuropil production
    2. Poorly differentiated NB (PD-NB):
      • Mildly differentiated neuroblastic cells (<5% of tumor cells)
      • Neuropil production present
    3. Differentiating NB (D-NB):
      • ≥5% differentiated neuroblastic cells
      • Neuropil production present
  • MKI is applied to only NB.

Mitosis-Karyorrhexis Index (MKI)

Yellow circles: mitosis; red circles: karyorrhexis
  • Only used for NB (including NB component in GNB nodular)
    • Count 5000 cells!!
    • Take an average from multiple areas
  • Low: <100/5000 cells (<2%)
  • Intermediate: 100-200/5000 cells (2-4%)
  • High: ≥200/5000 cells (≥4%)

2. Ganglioneuroblastoma (GNB) subtype

  • Ganglioneuroblastoma, intermixed (GNB, Schwannian stroma-rich form, ≥50%)
    • Islands of neuroblastic cells + neuropil
    • Abundant Schwannian-stroma background
  • Nodular GNB is a form of GNB.
    • More than one clone with a Schwannian stroma-poor (NB) component and rich/predominant (GNB/GN) component.

3. Ganglioneuroma (GN) subtype

  • Ganglioneuroma (GN, Schwannian stroma-dominant form, of course ≥50%)
  • The most mature subtype with:
    • Maturing/matured neuroblastic cells = ganglion cells
    • Neuropil production is no longer identified.

Favorable and Unfavorable Histology

  • Favorable histology (FH) – age-appropriate differentiation
  • Unfavorable histology (UH) – not appropriately differentiated for age
    Favorable histology shows appropriate tumor differentiation for age.
    INPC: Cheat Sheet (Click below to get a free PDF!)
    NB Cheat SheetDownload

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