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The ICD-O-3.2 Implementation Guidelines and ICD-O-3.2 Coding Table indicate that insulinoma, NOS has changed behavior from /0 to /3 for cases diagnosed 2021 and later. However, the ICD-O-3.2 Implementation Guidelines do not indicate whether this change applies to tumors described as above. Insulinomas are generally neuroendocrine tumors/neoplasms, so it seems any neuroendocrine tumor described as an insulinoma should be collected as 8151/3, but does that apply to an epithelioid tumor/neoplasm also described as insulinoma?

This question was prompted from preparing SEER*Educate coding exercises. We will use the answer as a reference in the rationales.

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?

SEER Program Coding and Staging Manual: Reportability – Reportable Diagnosis List indicates pancreatic intraepithelial neoplasia (PanIN II) (C250-C259) is reportable.

However, the ICD-O-3.2 lists “Glandular intraepithelial neoplasia, grade II” and “Glandular intraepithelial neoplasia, low grade” as histology code 8148 with behavior of /0 (benign).

Insulinoma, NOS is reportable for cases diagnosed 2021 and later. However, the diagnosis of insulinoma is most frequently made with clinical correlation of the patient's clinical syndrome and serum hormone levels. Despite a pathological diagnosis of NET, this will clinically be stated as insulinoma based on the functional type of tumor. At the largest facility in our area, all pathology reports with a diagnosis of insulinoma over the last year only provide a pathological Final Diagnosis of NET (either G1 or G2), but elsewhere specify, Functional Type: Pancreatic neuroendocrine tumor, functional. Correlation with Clinical Syndrome and Elevated Serum Levels of Hormone Product: Insulin-producing (Insulinoma).

For 2021 and later, it seems this should be accessioned as insulinoma (8151/3), but one cannot arrive at that histology using the current Other Sites (MP/H) H Rules. Following the existing rules, one would code the histology to NET, G1 or NET, G2 (8240 or 8249) per Rule H6. There are technically two specific histologies to consider: NET (either 8240 or 8249) and insulinoma, NOS (8151). Following the H Rules, Rule H6 instructs one to code the histology with the numerically higher ICD-O-3 code (8240 or 8249).

Coding this histology to NET (8240 or 8249) does not seem to reflect the most accurate classification of this tumor, but applying the current rules, this is the only histology that can be coded. There is no current guideline in the Other Sites schema or the ICD-O-3.2 Implementation Guidelines instructing us to ignore the pathological diagnosis of a NET for these tumors (even though insulinomas are NETs). The only SINQ that currently exists (SINQ 20150019) states the histology can be coded as either a NET or an insulinoma in these cases. How are registrars to consistently code histology for these tumors without a rule clarification?

This question was prompted from preparing SEER*Educate coding exercises. We will use the answer as a reference in the rationales.

1) CT scan: Cystic lesion in body of pancreas. Discharge dx: pancreas ca.

2) Discharge dx: CBD obstruction due to probable early ca in head of pancreas.

3) CT scan: mass involves the head and body of the pancreas. No evidence of abdominal mets. Discharge dx: Locally advanced pancreatic ca.

4) H&P: Pt with splenomegaly probably secondary to splenic vein thrombosis and a large ca of the tail of pancreas. Imp: Advanced pancreatic ca of the tail of pancreas. Would you code extension to splenic vein [56]?

5) H&P: Pancreatic ca with extension or mets into porta hepatis. (Would you assume direct extension or mets?)

6) CT scan: Pancreas ca. Significant peritoneal implants. (Would you assume the implants to be related to the pancreas primary and code as involvement?)