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SEER Inquiry System - Report
Produced: 09/17/2025 9:31 PM
Question 20230019
Inquiry Details
References:
#1: Solid Tumor Rules. Other Sites, March 2023 update
#2: WHO Class Digest System Tumors, 295-372. Chapter 10-Tumors of the pancreas
Question:
Solid Tumor Rules/Multiple Primaries--Pancreas: How many primaries, and what M Rule applies, when a pancreatectomy identified an invasive adenocarcinoma in one pancreatic head tumor, but multiple separate pancreatic neuroendocrine tumors (PanNETs), WHO grade 1, in the pancreatic body? See Discussion.
Discussion:
There was a 3.5 cm invasive adenocarcinoma tumor in the pancreatic head. There were four separate, sized pancreatic neuroendocrine tumors measuring 0.9, 0.7, 0.5 and 0.2 cm in the pancreatic body. There are multiple tumors with distinctly different histologies. However, Table 11 (Pancreas Histologies) does not include any entries for neuroendocrine tumors of the pancreas (e.g., pancreatic NET, WHO grade 1, histology 8240). While it would seem Rule M19 should apply as they’re distinctly different histologies, because PanNETs are not included in Table 11, it is not clear which M Rule applies to these multiple tumors.
If Rule M19 does not apply, we are left with Rule M21 (Abstract a single primary when there are multiple tumors that do not meet any of the above criteria). Are these separate tumors with distinctly different histologies really a single primary? Pancreatic neuroendocrine tumors are not an uncommon histology, is there a reason these were not included in Table 11?
Answer:
Abstract two primaries using the 2023 Solid Tumor Rules, Other Sites, Rule M19, as adenocarcinoma and pancreatic neuroendocrine tumors are two distinct histologies. The WHO Classification of Digestive Tumors, 5th ed., Chapter 10-Tumors of the Pancreas, lists both epithelial tumors and neuroendocrine neoplasm as separate entities. The Solid Tumor Rules histology-specific tables contain histologies that commonly occur in the 19 site-specific histology tables; therefore, not all histologies are listed in the rules. Further, the adenocarcinoma would be staged in the Pancreas Schema, while the neuroendocrine tumor would be staged in the NET Pancreas schema.
We will consider adding PanNETs to Table 11 in a future release of the Solid Tumor Rules.
