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We are increasingly seeing pathologists use this terminology to describe WHO G2 meningiomas, but the histology term "Atypical meningioma" is not being used, and a more specific "Histological Classification" of other WHO Grade 2 meningiomas (i.e., chordoid or clear cell meningioma) is not given. Can the combination of meningioma, WHO Grade 2 plus the histological classification listing multiple features of an atypical meningioma be used to code morphology to 9539/1? Or is this just a meningioma, NOS 9530/0 despite the WHO Grade 2 classification?

The term “poorly differentiated carcinoma (NOS)” is listed as related to “undifferentiated carcinoma (NOS)” in the ICD-O 3.2. It is also listed in the Solid Tumor Rules for Urinary Table 2 (Urinary subtypes), Other Sites Table 16 (uterine corpus primaries) and Table 19 (vulvar primaries).

Are these the only sites in which one should code “poorly differentiated carcinoma (NOS)” as 8020 (undifferentiated carcinoma)?

How is histology coded if the only microscopic confirmation is from a metastatic site showing “poorly differentiated carcinoma” (NOS) or “invasive carcinoma, poorly differentiated” (NOS)?

Example 1: Primary pancreatic cancer diagnosed on imaging and confirmed with liver mets core biopsy showing “poorly differentiated carcinoma.” Immunostaining pattern was non-specific. No further workup or treatment was planned.

Other Sites - Table 11 (Pancreas Histologies) includes undifferentiated carcinoma (8020/3) as a valid histology; however, the synonyms/subtypes/variants do not mention poorly differentiated carcinoma. How should histology be coded for this case?

Example 2: Hemicolectomy with cecal tumor final diagnosis of “invasive carcinoma, poorly differentiated” and synoptic summary listing “Histologic type: Invasive carcinoma. Histologic grade: G3 of 4: poorly differentiated.”

Colorectal Table 1 (Specific Histologies and Subtypes/Variants) includes undifferentiated adenocarcinoma/carcinoma 8020 as a subtype of adenocarcinoma NOS. There is no mention of poorly differentiated in this context. How should histology be coded for this case?

An argument could be made to apply Rule M10 (timing rule which may result in reporting the case as an additional primary) because the 2022 primary included multiple non-invasive urothelial carcinoma tumors in both the bladder and other urinary sites (coded to site C689, not C679) following a long disease-free interval. While Rule M10 excludes multiple bladder tumors, does that also apply when new, multifocal urothelial tumors arise in both bladder and other urinary sites? Does the presence of any subsequent bladder tumor rule out the use of M10 and one must use M11 that indicates reporting this disease process is a single primary?

10/2017 Bladder cancer diagnosed as invasive papillary urothelial bladder carcinoma (8130/3) (submucosal invasion).

12/2017 Surveillance scope and transurethral resection of bladder tumor (TURBT) finds “recurrent” bladder tumor, non-invasive papillary urothelial bladder carcinoma (8130/2) - same primary per 2007 Multiple Primaries/Histology, Rule M6, (both papillary urothelial bladder carcinomas).

4/2018 Radical nephrectomy found focally invasive urothelial carcinoma (8120/3) in the renal pelvis.

Is this a new primary per 2018 and forward STR, Rule M6, because it was more than 60 days since the 12/2017 in situ bladder recurrence? Or would one compare the 2018 diagnosis to the original invasive bladder tumor in 10/2017, and continue on to Rule M11, which says to abstract a single primary for urothelial carcinomas in multiple organs, regardless of behavior?

SINQ #20120080 said to compare to the original diagnosis and disregard intervening recurrences, but that pertained to the 2007 MP/H rules. Does this still apply for 2018 forward? STR, Rule M10, Note 3, states when there is a recurrence within three years of diagnosis, the “clock” starts over. The time interval is calculated from the date of last recurrence. Comparing each recurrence for urothelial carcinomas using Rule M6 could result in over-counting them. Can the instructions on how to calculate the 60-day interval be clarified in Rule M6?

The patient underwent a gross total resection of the 2005 glioblastoma multiforme (9440/3). The patient was subsequently diagnosed with a 2024 diagnosis of astrocytoma, IDH-mutant, WHO grade 4 (9445/3).

Should Rule M13 apply to the new 2024 diagnosis and a new primary be accessioned because astrocytoma, IDH-mutant, WHO grade 4 is listed on a different row than glioblastoma? It is unclear whether histology 9445 should be classified as being on a different row because it is also listed as a subtype/variant for glioblastoma in Table 3. Table 3 lists histology 9445 as both “Astrocytoma, IDH-mutant, WHO grade 4” and as “Glioblastoma IDH-mutant.”

Malignant Central Nervous System (CNS) Rule M5 instructs us to abstract a single primary (as malignant) when a single tumor is originally diagnosed as non-malignant, the “First course treatment was active surveillance (no tumor resection),” and the subsequent resection pathology is malignant.

This patient’s first course of treatment was not active surveillance. While the patient did not have first course tumor resection, the tumor was treated with Cabergoline.

Should Rule M5 apply because there was no tumor resection? If so, should Rule M5 clearly state no tumor resection is the criteria (not active surveillance)?

SINQ 20230023 does indicate a PitNET diagnosis following a diagnosis of pituitary adenoma does not fall into standard rules, but in the previous SINQ the first course treatment was a partial resection.

It is unclear whether other types of treatment could result in a new malignant PitNET, following a previously treated non-malignant pituitary tumor.

The patient has two, separate, non-contiguous tumors. One tumor is a benign meningioma and the other is a malignant oligodendroglioma.

The original plan was not to treat the asymptomatic meningioma. However, after worsening symptoms, imaging and resection proved a separate left frontal lobe malignant tumor.

Rule M5 is the only M Rule in the Malignant CNS Multiple Primary Rules, Multiple Tumors module that addresses separate non-malignant and malignant tumors. This rule provides only two criteria to follow when a malignant tumor follows a non-malignant tumor. The first criteria (for non-malignant tumor followed by malignant tumor) states:

--Patient had a resection of the non-malignant tumor (not the same tumor) OR

--It is unknown/not documented if the patient had a resection.

This patient did not have a resection of the original, separate, non-malignant tumor, but the treatment plan was known to not include a resection. Should Rule M5 also apply to cases where the patient never had treatment planned for the separate non-malignant tumor?

The patient underwent a resection of the transitional meningioma in 2012, but residual tumor was left behind. The patient was on surveillance until imaging showed growth of the residual tumor. The resection in 2022 proved atypical meningioma.

Rule M2, the first rule that applies, indicates this situation represents a single primary (a single tumor). However, Rule M4 states the transformation from a benign meningioma to a borderline meningioma would only be a single primary if the meningioma was a NOS.

This patient has microscopic confirmation of a meningioma showing different subtypes/variants (listed in Column 3, Table 6). Should this be accessioned as multiple primaries based on the transformation and distinctly different histologies?

Historically, synchronous ductal and lobular tumors have been accessioned as a single primary. These were previously covered under Rule M10, which was removed from the (STR) Manual 2026 Update. While the previous iteration of Rule M10 was problematic, the main issue related to the lack of a timing component within the rule (i.e., indicating it applied to synchronous ductal and lobular tumors).

Using the current Breast STR, when there are two (or more) simultaneous tumors which are not mixed lobular and ductal within each tumor, the applicable M Rule is Rule M13: Abstract multiple primaries when separate/non-contiguous tumors are on different rows in Table 3. To apply the M Rules, a provisional histology must be assigned to EACH tumor so we cannot code each tumor as 8522 before we start applying the M Rules. These provisional histologies would be 8500 and 8520, and these are on different rows in Table 3.