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TNM staging of colorectal neuroendocrine tumors (AJCC 8th edition)

Author: Raul S. Gonzalez, M.D. (see Authors page)

Revised: 9 May 2018, last major update May 2018

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed search: Staging[TIAB] colorectal neuroendocrine tumors

Cite this page: Gonzalez, R.S. TNM staging of colorectal neuroendocrine tumors (AJCC 8th edition). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumorstagingneuroendocrine.html. Accessed May 23rd, 2018.

Pathologic TNM staging of neuroendocrine tumors of the colorectum, AJCC 8th edition
Definition / general
  • Well differentiated neuroendocrine tumors of the colorectum ("carcinoids") are covered by this staging system
  • Not covered by this staging system are poorly differentiated neuroendocrine carcinomas at this location (use the adenocarcinoma staging system instead)
  • Appendix tumors have their own separate staging system
Essential features
Terminology
  • "Carcinoid" is no longer an acceptable term
ICD-10 coding
  • C7A.02: Malignant carcinoid tumors of the appendix, large intestine and rectum (with subcodes depending on exact anatomic location)
Primary tumor (pT)
  • TX: Primary tumor cannot be assessed
  • T0: No evidence of primary tumor
  • T1: Tumor invades the lamina propria or submucosa and is ≤ 2 cm
    • T1a: Tumor < 1 cm in greatest dimension
    • T1b: Tumor 1 - 2 cm in greatest dimension
  • T2: Tumor invades the muscularis propria or is > 2 cm with invasion of the lamina propria or submucosa
  • T3: Tumor invades through the muscularis propria into subserosal tissue without penetration of overlying serosa
  • T4: Tumor invades the visceral peritoneum (serosa) or other organs or adjacent structures
Regional lymph nodes (pN)
  • NX: Regional lymph nodes cannot be assessed
  • N0: No regional lymph node metastasis has occurred
  • N1: Regional lymph node metastasis

  • Notes: Regional lymph nodes vary based on the precise lesional site within the colorectum but overall can include pericolic, ileocolic, right colic, middle colic, left colic, sigmoid, inferior mesenteric, superior rectal, inferior rectal, mesorectal and internal iliac nodes
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 metastases
Prefixes
  • r: recurrent tumor stage
Stage grouping
Stage I: T1 N0 M0
Stage IIA: T2 N0 M0
Stage IIB: T3 N0 M0
Stage IIIA: T4 N0 M0
Stage IIIB: any T N1 M0
Stage IV: any T any N M1
Registry data collection variables
  • Tumor site
  • Size of tumor
  • Depth of invasion
  • Nodal status and number of nodes involved, if applicable
  • Sites of metastasis, if applicable
  • Ki67 index
  • Mitotic count
  • Histologic grade
Histologic grade
  • Grading is not formally part of the staging system
  • Most pathologists use the ENETS / WHO grading criteria:
    • Grade 1: Mitotic rate < 2 per 10 high power fields and Ki67 rate < 3%
    • Grade 2: Mitotic rate 2 - 20 per 10 high power fields or Ki67 rate 3 - 20%
    • Grade 3: Mitotic rate > 20 per 10 high power fields or Ki67 rate > 20%
Histopathologic type
  • Well differentiated neuroendocrine tumor, grade 1
  • Well differentiated neuroendocrine tumor, grade 2
  • Well differentiated neuroendocrine tumor, grade 3
Board review question #1
Rectal neuroendocrine neoplasm with salt and pepper nuclei, no necrosis, a mitotic rate of 1 per 10 high power fields and a Ki67 index of 25% is best classified as:

  1. Poorly differentiated neuroendocrine carcinoma
  2. Well differentiated neuroendocrine tumor, grade 1
  3. Well differentiated neuroendocrine tumor, grade 2
  4. Well differentiated neuroendocrine tumor, grade 3
Board review answer #1
D. Well differentiated neuroendocrine tumor, grade 3