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Cite this page: Gonzalez RS. Staging-neuroendocrine. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorstagingneuroendocrine.html. Accessed April 29th, 2025.
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
- AJCC 7th edition staging was sunset on December 31, 2017; as of January 1, 2018, use of the 8th edition is mandatory
- AJCC 9th edition was released in 2023, with minimal changes from the 8th edition
Terminology
- Carcinoid is no longer an acceptable term
ICD coding
- ICD-10: 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 mucosa or submucosa and is ≤ 2 cm in greatest dimension
- T1a: tumor ≤ 1 cm in greatest dimension
- T1b: tumor > 1 cm but ≤ 2 cm in greatest dimension
- T2: tumor invades the muscularis propria or is > 2 cm with invasion of the mucosa 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 tumor involvement of regional lymph node(s)
- N1: tumor involvement of regional lymph node(s)
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
Prefixes
- c: clinical
- p: pathological
- yc: posttherapy clinical
- yp: posttherapy pathological
Primary tumor suffix
- (m): multiple synchronous primary tumors
Regional lymph nodes suffix
- (f): fine needle aspiration (FNA) or core needle biopsy
AJCC prognostic stage groups
| Stage I: | T1 | N0, NX | 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
|
Prognostic tumor characteristics
- Mitotic count
- Ki67 index
- Plasma or urinary 5-hydroxyindoleacetic acid (5-HIAA) level
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
- Lymphovascular invasion
- Margin status
Emerging factors for data collection
Histologic grade (G)
- G1: mitotic rate < 2 per 2 mm2 and Ki67 < 3%
- G2: mitotic rate 2 - 20 per 2 mm2 or Ki67 3 - 20%
- G3: mitotic rate > 20 per 2 mm2 or Ki67 > 20%
Histopathologic type
- Neuroendocrine tumor, NOS
- Neuroendocrine tumor, grade 1
- Neuroendocrine tumor, grade 2
- Neuroendocrine tumor, grade 3
- L cell neuroendocrine tumor
- Glucagon-like peptide producing neuroendocrine tumor
- PP / PPY (pancreatic polypeptide) producing tumor
- Enterochromaffin cell (EC cell) neuroendocrine tumor
- Serotonin producing neuroendocrine tumor
Residual tumor (operative factor)
- R0: complete resection, margins histologically negative, no residual tumor left after resection
- R1: incomplete resection, margins histologically involved, microscopic tumor remains after resection of gross disease (relevant to resection margins that are microscopically involved by tumor)
- R2: incomplete resection, margins involved or gross disease remains
Practice question #1
Which of the following is the best classification for a rectal neuroendocrine neoplasm with salt and pepper nuclei, no necrosis, a mitotic rate of 1 per 2 mm
2 and a Ki67 index of 25%?
- Poorly differentiated neuroendocrine carcinoma
- Well differentiated neuroendocrine tumor, grade 1
- Well differentiated neuroendocrine tumor, grade 2
- Well differentiated neuroendocrine tumor, grade 3
Practice answer #1
D. Well differentiated neuroendocrine tumor, grade 3. The Ki67 index is sufficiently high that the tumor qualifies as grade 3 per WHO criteria. Answer A is incorrect because the histologic findings are not typical for neuroendocrine carcinoma. Answer B is incorrect because for grade 1 tumors, Ki67 index is < 3% and mitotic rate is < 2 per 2 mm
2. Answer C is incorrect because for grade 2 tumors, Ki67 index is 3 - 20% or mitotic rate is 2 - 20 per 2 mm
2.
Comment here
Reference:
Colon - Staging-neuroendocrine
Practice question #2
Which of the following describes a well differentiated neuroendocrine tumor of the rectum staged as pT1b?
- Tumor ≤ 1 cm in greatest dimension
- Tumor > 1 cm but ≤ 2 cm in greatest dimension
- Tumor > 2 cm with invasion of the mucosa or submucosa
- Tumor invading muscularis propria
Practice answer #2
B. Tumor > 1 cm but ≤ 2 cm in greatest dimension. This is the criteria for pT1b well differentiated neuroendocrine tumors in the colorectum. Answer A is incorrect because it describes pT1a disease. Answers C and D are incorrect because they describe pT2 disease.
Comment here
Reference:
Colon - Staging-neuroendocrine
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