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The 2021 ICD-O-3.2 Update includes papillary microcarcinoma (8341/3) as the preferred term for thyroid primaries (C739). However, there are multiple SINQ entries instructing registrars not to use code 8341/3 for diagnoses of micropapillary carcinoma of the thyroid (including SINQ 20071076, 20081127, 20110027, 20150023, and 20180008).

SINQ 20150023 specifically indicates: Per the WHO Tumors of Endocrine Organs, for thyroid primaries/cancer only, the term micropapillary does not refer to a specific histologic type. It means that the papillary portion of the tumor is minimal or occult (1 cm or less in diameter) and was found incidentally. WHO does not recognize the code 8341 and classifies papillary microcarcinoma of the thyroid as a variant of papillary thyroid carcinoma and codes histology to 8260. If the primary is thyroid and the pathology states papillary microcarcinoma or micropapillary carcinoma, code 8260 is correct.

Does this clarification apply to cases diagnosed 2021 and later? If WHO feels the term micropapillary still does not refer to a specific histologic type for the thyroid, why is 8341/3 listed as a preferred term for this morphology/site combination? For cases 2021 and later, should a diagnosis of Incidental papillary thyroid microcarcinoma (3 mm) in left lower pole, be coded as 8341/3 per the ICD-O-3.2, or as 8260/3 per clarification in multiple SINQ entries?

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

The 2018 Solid Tumor (ST) Rules General Rules state: For those sites/histologies which have recognized biomarkers, the biomarkers frequently identify the histologic type. Currently there are clinical trials being conducted to determine whether these biomarkers can be used to identify multiple primaries. Follow the Multiple Primary Rules; do not code multiple primaries based on biomarkers.

Additionally, Biomarkers is at the top of the priority order to identify histology in several sections (it appears to be excluded from only Colon, Melanoma and Other sections). In the sections that include this rule, there is not much additional information on using biomarkers. Can you please provide further explanation for prioritizing biomarkers in the histology coding rules? For example, will the ST manual be updated when we need to look for specific biomarkers in a diagnosis?

The Equivalent Terms and Definitions sections in the Solid Tumor Rules for these schemas identify which sites must have laterality coded, but there is no instruction for coding laterality when bilateral tumors are a single primary. The SEER Manual currently only indicates code 4 (bilateral) is seldom used (e.g., bilateral ovarian tumors, Wilms tumors, etc.) but does not indicate laterality code 4 should be used for CNS tumors. Is this note going to be updated or should a non-bilateral code be applied?

Example: MRI demonstrates multiple left-sided dural-based meningiomas including a 4.4 cm left posterior fossa meningioma, a 0.8 cm left frontal-parietal meningioma and a right posterior frontal meningioma. The large left posterior fossa meningioma was resected and proved atypical meningioma. Should the laterality be 4 (bilateral) as the patient had both left and right-sided meningiomas confirmed to be a single primary? Or should the laterality be coded as 2 (left) since only the large left-sided meningioma was proven to be a borderline tumor (atypical meningioma, 9539/1) and the others were benign?

7/8/16 Urinary bladder, biopsy: Non-invasive low grade papillary urothelial carcinoma. Muscularis propria (detrusor muscle) is not identified.

9/2/16 Urinary bladder, bladder tumor, transurethral resection: High grade papillary urothelial carcinoma. No definite invasion identified. Muscularis propria (detrusor muscle) is identified and not involved by tumor.

1/7/17 A\S\Bladder: Noninvasive low grade papillary urothelial carcinoma. Granulomatous cystitis, consistent with BCG (Bacillus Calmette-Guerin) treatment. Lamina propria is not involved with tumor. Detrusor muscle is not identified.

4/4/17 Dome: Papillary urothelial carcinoma, low grade. No evidence of invasion. Muscularis propria is not present.

Patient is clearly followed for at least a year but no further information until 19 months later, 11/14/18, when biopsy of lung indicates metastatic disease.

11/14/18 Lung, right lower lobe, mass, biopsy: Metastatic urothelial carcinoma. Immunohistochemical analysis results (CK7 positive, CK20 focally positive, P63 positive, GATA3 positive, TTF1 negative and NAPSIN-A negative) support the diagnosis

Rule M11 states: Abstract a single primary when there are urothelial carcinomas in multiple urinary organs, but neither the Rule nor the Notes describe the timing of these multiple urinary organ carcinomas. Timing requirements for other rules are clearly stated.

Does Rule M11 have a timing requirement or is it intended to apply to all urothelial carcinoma tumors regardless of timing (and not already qualifying for application of a previous M rule)?

The Solid Tumor Rules indicate bladder tumors that are urothelial carcinoma (8120) and small cell carcinoma (8041) are separate primaries per Rule M13 (Abstract multiple primaries when separate/non-contiguous tumors are on different rows in Table 2). These are distinctly different histologies and, presumably, one would want to capture the small cell carcinoma (or small cell carcinoma component) as this has a worse prognosis.

However, if a subsequent bladder tumor is composed of invasive urothelial carcinoma and small cell neuroendocrine carcinoma, the histology is coded as 8045/3 per Rule H4, but this is not abstracted as a multiple primary. The only M Rule that applies is Rule M18 (Abstract a single primary when tumors do not meet any of the above criteria). The mixed histology code 8045 is not included in Table 2, so none of the histology-based M Rules apply. Is the subsequent mixed invasive urothelial and small cell carcinoma tumor (8045/3) the same primary as a previously diagnosed invasive urothelial carcinoma (8120/3) when these tumors are diagnosed within three years?

Glioblastoma multiforme is listed as a synonym for the preferred term glioblastoma, NOS (9440) per Table 3 Column 2. Therefore, it seems reasonable to assume that a diagnosis of glioblastoma, NOS would be a new primary if it followed a glial or astrocytic tumor. However, in general, the Solid Tumor Rules use the preferred terminology and/or indicate when a specific rule also includes any tumor diagnosed as a subtype/variant. Rule M6 does not explicitly include a diagnosis of glioblastoma, NOS or any of its subtypes/variants (e.g., glioblastoma IDH-mutant or gliosarcoma). Does Rule M6 apply to any diagnosis of glioblastoma, NOS and any of its synonyms or subtypes/variants?

The patient has one tumor each in the left parietal and left medial temporal lobe. The tumors were excised. The final diagnosis for the left parietal tumor is glioblastoma, IDH-wild type. he final diagnosis of the left medial temporal tumor is, at least anaplastic astrocytoma, WHO grade III; see comment. The comment states: There is a single focus of vascular hyperplasia, separate from neoplastic cells. No necrosis is identified. These findings on their own would warrant a diagnosis of anaplastic astrocytoma, WHO grade III. However, in the context of the patient's glioblastoma in the left parietal lobe, and imaging showing ring-enhancing lesions of the parietal and temporal lobes, this specimen is favored to be an un-sampled glioblastoma, WHO grade IV. The Solid Tumor Rules indicate we may no longer use terms like favor(s) to code the histology, leaving the final diagnosis as the priority source for coding histology per the Histology coding rules.

The tumor board review confirmed that, despite the anaplastic astrocytoma on pathology, they felt strongly that this is a multifocal glioblastoma and not an anaplastic astrocytoma. Both the pathologist's comment and the tumor board's assessment indicate this patient does not have two primaries. However, the Solid Tumor Rules do not give priority to the tumor board's assessment over the pathology, and registrars are not to use ambiguous terms to code histology thus leaving the two histologies to consider. Per the Solid Tumor Rules, one tumor that is glioblastoma and one tumor that is anaplastic astrocytoma are multiple primaries per M11 (Abstract multiple primaries when separate, non-contiguous tumors are on different rows in Table 3 in the Equivalent Terms and Definitions. Timing is irrelevant).

As a central registry, we cannot ask the pathologist or attending physician for clarification as suggested in Section 3 of the Malignant CNS and Peripheral Nerves Equivalent Terms and Definitions. We can only follow the current Solid Tumor Rules. In doing so, we would have to ignore both the pathologist's and tumor board's assessment that this patient has multifocal glioblastoma. Is there any concern that this will lead to over-reporting?

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.

Patient has a 1.7 cm encapsulated papillary carcinoma staged as pTis located 2 cm from the nipple and Paget disease of the nipple on mastectomy pathology.

There is no indication in Table 3: Specific Histologies, NOS/NST, and Subtypes/Variants that encapsulated papillary carcinoma is a subtype of ductal carcinoma. Rule M8 notes that if the histology of the underlying tumor is any histology OTHER THAN duct or subtypes of duct, one should continue through the rules. But if M9 applies to this case, then incidence reporting will be increased in comparison to prior years.