Staging-neuroendocrine tumors

Deputy Editor-in-Chief: Debra L. Zynger, M.D.
Raul S. Gonzalez, M.D.

Last author update: 10 December 2020
Last staff update: 6 May 2021

Copyright: 2018-2024,, Inc.

PubMed Search: Appendix TNM staging of neuroendocrine tumors

Raul S. Gonzalez, M.D.
Page views in 2023: 2,561
Page views in 2024 to date: 308
Cite this page: Gonzalez RS. Staging-neuroendocrine tumors. website. Accessed February 26th, 2024.
Definition / general
  • All well differentiated neuroendocrine tumors of the appendix, regardless of grade, are covered by this staging system
  • Not covered by this staging system are appendiceal adenocarcinomas, goblet cell carcinoids and poorly differentiated neuroendocrine carcinomas (use the appendix carcinoma staging system instead)
Essential features
ICD coding
  • ICD-10: C7A.020 - Malignant carcinoid tumor of the appendix
Primary tumor (pT)
  • TX: Primary tumor cannot be assessed
  • T0: No evidence of primary tumor
  • T1: Tumor ≤ 2 cm in greatest dimension
  • T2: Tumor > 2 cm but ≤ 4 cm
  • T3: Tumor > 4 cm or with subserosal invasion or involvement of the mesoappendix
  • T4: Tumor perforates the peritoneum or directly invades other adjacent organs or structures (excluding direct mural extension to adjacent subserosa of adjacent bowel), e.g. abdominal wall and skeletal muscle
Regional lymph nodes (pN)
  • NX: Regional lymph nodes cannot be assessed
  • N0: No regional lymph node metastasis
  • N1: Regional lymph node metastasis
  • Notes: the ileocolic nodes are the regional nodes for this staging
Distant metastasis (pM)
  • M0: No distant metastasis
  • M1: Distant metastasis
    • M1a: Metastasis confined to liver
    • M1b: Metastasis in at least one extrahepatic site (e.g. lung, ovary, nonregional lymph node, peritoneum, bone)
    • M1c: Both hepatic and extrahepatic metastasis
  • r: recurrent tumor
Stage grouping
Stage I: T1 N0 M0
Stage II: T2 - 3  N0 M0
Stage III: T4 N0 M0
any T N1 M0
Stage IV:any T any N  M1
Registry data collection variables
  • Size of tumor
  • Depth of invasion
  • Invasion of mesoappendix
  • Number of nodes involved, mesenteric mass, mesenteric vessel encasement
  • Perineural invasion
  • Lymphovascular invasion
  • Sites of metastasis, if applicable
  • Type of surgery
  • Ki67 proliferative index
  • Mitotic count
  • Histologic grading (from Ki67 and mitotic count): G1, G2, G3
Histologic grade
  • Grading is not formally part of the staging system
  • Most pathologists use the European Neuroendocrine Tumor Society (ENETS) / World Health Organization (WHO) grading criteria:
    • Grade 1: Mitotic rate < 2 per 10 high power fields and Ki67 < 3%
    • Grade 2: Mitotic rate 2 - 20 per 10 high power fields or Ki67 3 - 20%
    • Grade 3: Mitotic rate > 20 per 10 high power fields or Ki67 > 20%
Histopathologic type
  • Well differentiated neuroendocrine tumor, G1 / G2 / G3
Board review style question #1
Which of the following factors affect the staging of appendiceal neuroendocrine tumors?

  1. Ki67 index and extent of local spread
  2. Ki67 index and mitotic rate
  3. Size and extent of local spread
  4. Size and Ki67 index
Board review style answer #1
C. Size and extent of local spread

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Reference: Staging-neuroendocrine tumors
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