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SEER Inquiry System - Report
Produced: 02/12/2026 7:16 AM
Question 20190025
Inquiry Details
References:
WHO Class Digest System Tumors
Question:
2018 Solid Tumor Rules/Histology--Colon: What is the histology code of a diagnosis of well differentiated neuroendocrine tumor (NET), grade 2 of the appendix? See Discussion.
Discussion:
SINQ 20160023 and the Solid Tumor Rules indicate NET G1 (or well differentiated NET) is coded as 8240 and NET G2 is coded as 8249.
Clarification regarding grade coding in the CAnswer Forum indicates well differentiated neuroendocrine tumor refers to the histologic type, and not the grade. Therefore, the term well differentiated is ignored for the purpose of grade coding.
Neither of these sources clarifies how to code histology for a tumor diagnosed as well differentiated neuroendocrine tumor, grade 2.
Answer:
Assign histology code 8249 for histology described as well differentiated NET G2. A synonym for NET of the appendix includes well-differentiated endocrine tumor/carcinoma according to WHO Classification of Tumors of the Digestive System, 4th edition. "Well differentiated" could apply to either NET G1 or NET G2.
