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The Summary Cancer Data does not seem to describe a more specific histology, but it does describe the tumor histology with the worst outcome and the most extensive tumor. The anaplastic carcinoma grossly extended into skeletal muscle and gave rise to multiple regional lymph node metastases. The more appropriate histology seems to be 8021.

However, current MP/H Rules for a single tumor indicate the histology should be coded to the numerically higher histology code (8260). Coding the histology to 8260 does not account for the more aggressive tumor. Should this histology be 8260 or 8021?

The synoptic report calls this “Invasive adenocarcinoma with secondary Paget disease of anal mucosa and perianal skin.” The tumor size is listed as “2.1 x 1.7 x 0.7 cm, including associated advanced adenoma; size does not include the extent of the associated Paget disease, which extends for at least 2 cm distally.”  Clinically this is called an incidentally discovered Paget’s disease.

It is unclear if this is a collision tumor that should be abstracted as separate primaries, or if this is a single tumor with underlying Paget’s disease (similar to that described in Other Sites Rule H26). If this is a single rectal tumor, there does not appear to be an H rule for this scenario.

The term "non-invasive follicular thyroid neoplasm with papillary-like nuclear features" is now being used, instead of the previous classification of an encapsulated malignant thyroid tumor. Recent evidence supports a very minimal risk of aggressive behavior for these tumors, and pathologists in our area are no longer classifying these as malignant in the final diagnosis.

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?

The terminology for carcinoid tumors has changed. The current terminology used is "neuroendocrine tumor." Are well-differentiated neuroendocrine tumors of the appendix non-reportable because carcinoid, NOS of the appendix has a borderline behavior code [8240/1]? When the histology/behavior codes for the term "well-differentiated neuroendocrine tumor" became 8240/3, did SEER intend this change to also apply to appendix primaries? If so, for which diagnosis year did this change go into effect?

The terms and definitions for "Brain" in the 2007 MP/H rules distinguish between pPNET and PNET. Is it correct even when the diagnostic terminology alone would lead to other coding, such as "PNET" used to diagnose a soft tissue mass in the chest and "neuroectodermal tumor" used to diagnose a brain mass?

Should additional rules be added to both "Brain" and "Other Sites" to enforce this distinction?

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.

The treatment regimen consisting of carfilzomib, lenalidomide, and dexamethasone (KRd) in SEER*Rx says not to code dexamethasone. I have a patient with multiple myeloma who received the KRd protocol in 2018 and the treatment regimen consisting of carfilzomib, daratumumab, and dexamethasone (KdD) (not in SEER Rx) in 2025. SEER RX says to code dexamethasone when it is given for multiple myeloma but also not to code dexamethasone when given as part of the KRd regimen (which is for multiple myeloma). I can follow the KRd instructions if that is what should take priority, but then would I code dexamethasone for the KdD regimen? KdD is not in SEER*Rx and it seems counterintuitive to code it for KdD and not for KRd.

The UroVysion website says that standard procedures, e.g., cytology, cystoscopy, take precedence over the UroVysion test. The Quest Diagnostics website says that "A positive result is consistent with a diagnosis of bladder cancer or bladder cancer recurrence, either in the bladder or in another site within the urinary system. A negative result is suggestive of the absence of bladder cancer but does not rule it out." Would we pick up the case if the UroVysion test was positive but the standard procedures were negative or non-diagnostic?

The WHO Blue Books do not include dedifferentiated carcinoma as a valid histology for the breast.  However, there is known to be progression of ductal carcinoma that is essentially dedifferentiation of an estrogen receptor, progesterone receptor, and HER2 breast carcinoma to a triple negative "dedifferentiated" carcinoma which it appears this patient has. Whether we should accession this as a separate 8020/3 primary per M14 is unclear and the Solid Tumor Manual does not address this scenario.