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The ICD-O-3.2 Coding Table includes Mullerian mixed tumor as the preferred term for histology code 8950 (previously malignant mixed Mullerian tumor/MMMT). This table also includes carcinosarcoma, NOS as the preferred term for histology code 8980. Neither the ICD-O-3.2 Coding Table nor the Implementation Guidelines address the long-standing issue of coding histology for diagnoses of carcinosarcoma/malignant mixed Mullerian tumor.

These endometrial primaries are frequently diagnosed as both carcinosarcoma and MMMT. The questions regarding histology coding for carcinosarcoma and carcinosarcoma/MMMT of the endometrium date back to before the Multiple Primaries/Histology Rules, with at least three SINQ entries instructing registrars not to use code 8950/3 (MMMT) for diagnoses of MMMT. SINQ has instructed registrars that MMMT is a synonym for carcinosarcoma and these tumors should be coded to 8980 (carcinosarcoma), not to 8950 (MMMT). The most recent SINQ is partly inconsistent with the others, indicating 8950 can be used if the tumor is only described as MMMT. The other SINQ entries state carcinosarcoma should be used as it is the preferred term for MMMT. (See SINQ 20061008, 20100009, 20180071.)

The most recent SINQ (20180071) specifically indicates: According to the WHO Classification of Tumors of Female Reproductive Organs, 4th edition, MMMT (8950/3) is now a synonym for carcinosarcoma (8980/3) even though it has a separate ICD-O code. The ICD-O code for MMMT is no longer in the WHO book. However, MMMT is in the ICD-O-3.2 Coding Table and is not stated to be obsolete or a synonym. Which is correct, the clarification in the SINQ or the 2021 ICD-O-3.2 Coding Table?

For a 2021 diagnosis of carcinosarcoma/malignant mixed Mullerian tumor, how should registrars code the histology? Follow the previous SINQ entries and Rule H17 to code the histology to 8980 when the diagnosis includes both carcinosarcoma and MMMT? Do these previous SINQ entries still apply to cases diagnosed 2021 and later?

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

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.

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.

Should the updated Note 5 from the Non-malignant CNS regarding optic nerve glioma also be incorporated into Note 6 for Malignant CNS rules (the pilocytic astrocytoma note)?

This was one of the major issues identified in the SEER*Educate Workshop. Registrars have demonstrated they do not consistently think to look at the Non-malignant CNS schema when they see the term glioma and continue to misclassify optic nerve gliomas as malignant.

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

Pituitary blastoma was not added to Table 3 (Specific Histologies, NOS, and Subtypes/Variants) of the 2018 Malignant CNS and Peripheral Nerves Solid Tumor Rules as part of the December 2020 update. This is a new malignant CNS histology for 2021 and later. Not including this histology in Table 3 results in the registrars being required to check another source to correctly code this histology. If this histology cannot be used for cases diagnosed prior to 2021, should that diagnosis year clarification be included in the STR?

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

Table 1 of the 2018 Kidney Solid Tumor Rules (STR) lists succinate dehydrogenase-deficient renal cell carcinoma as histology code 8312, but in the ICD-O-3.2 Coding Table it is listed as histology code 8311.

No changes were made in the Kidney STR. As a result, the histology change described in the ICD-O-3.2 Coding Table conflicts with Table 1. Succinate dehydrogenase-deficient renal cell carcinoma (SDHD) is listed in Table 1 as a synonym for renal cell carcinoma, NOS (8312). However, the ICD-O-3.2 Coding Table lists this as a related term for histology code 8311/3. This related term was not discussed in the Implementation Guidelines, and no change was noted in the STR.

While it seems we should continue to follow the STR, without clarification as to why this histology change was not implemented in STR, achieving consistency will be problematic if registrars jump straight to the ICD-O-3.2 Coding Table to code histology for cases diagnosed 2021 and later. If this code cannot be used for cases diagnosed prior to 2021, should that clarification be included in the STR?

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

First, reportability of clear cell papillary renal cell carcinoma changed from 8323/3 to 8323/1. Although it does not appear the standard-setters implemented this change, note of the conflict between the ICD-O-3.2 and the Solid Tumor Rules (STR) is not included in the Implementation Guidelines or STR. The current Note for clear cell papillary renal cell carcinoma (8323) was left in Table 1, so this presumably is still reportable. It would be helpful if the conflict with ICD-O-3.2 was addressed, especially since the existing Note refers to changes made back in 2016 (not 2018 or 2021).

Second, is the term sarcomatoid renal cell carcinoma still coded as a synonym for renal cell carcinoma (8312) because sarcomatoid is referring to a pattern of differentiation or 8318 (renal cell carcinoma, sarcomatoid)? The STR, Table 1, lists sarcomatoid renal cell carcinoma as 8312, but the ICD-O-3.2 lists this as 8318. The Note in Table 1 still indicates WHO/IARC and College of American Pathologists agree that sarcomatoid carcinoma is a pattern of differentiation, not a specific subtype, of renal cell carcinoma. This appears to conflict with WHO/IARC ICD-O-3.2 Coding Table as it provides a different, specific histology code for this malignancy. How can WHO/IARC classify this both a pattern of renal cell carcinoma and a separate, specific histology?

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

Lip has not been added to any of the site-specific histology tables, nor has any other instruction been provided for coding tumors in this site.

Coding histology for lip primaries is difficult because registrars do not know where to look first. The Solid Tumor Rules indicate one should use the tables first, but then do not inform registrars what table to use for a lip primary (i.e., a specific table, any table, no table).

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

The Terms and Definitions Introduction discusses how these are older terms, but pathologists may still use them. In our region, pathologists do, in fact, still use these terms. Can these terms be added to Table 1? For registrars who do not reference the Introduction every time they code histology but go directly to Table 1, coding consistency would likely improve if such terms were added in the Table.

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

Is an M rule needed to address multiple tumors and Note 2 in Table 3? Does Note 2 in Table 3 apply when multiple tumors exist and one tumor contains only ductal carcinoma?

The M Rules currently confirm that a metaplastic carcinoma (whether it is involved with ductal or lobular) and a separate ductal carcinoma are separate primaries because these histologies are on different rows in Table 3 (separate primaries per M14). There is no specific rule regarding metaplastic carcinomas in the Multiple Tumors (M Rules) module, so presumably, the presence of a separate ductal carcinoma is not lumped into Note 2 in Table 3 for metaplastic carcinoma.

However, the note is confusing when there are multiple tumors involved because it appears to the registrars there are two options for coding the histology. To some registrars, the rules indicate it does not matter if the tumor is predominantly ductal carcinoma as long as some percentage of metaplastic carcinoma is present, code histology to metaplastic carcinoma. For other registrars, the presence of solely a ductal carcinoma in a second tumor is a separate primary from the separate metaplastic carcinoma.

The M rules and Note 2 need to clarify this issue to promote consistency.

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