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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.

In our region, pathologists often describe histology using the term phenotype. However, the use of the term phenotype is not discussed in the Solid Tumor Manual.

Example: Final Diagnosis of a colon tumor is invasive adenocarcinoma with a mixed phenotype, and the Diagnosis Comment states: The majority of the disease is poorly differentiated/signet ring cell phenotype.

Would the histology be coded to 8490 (signet ring cell carcinoma), if the majority of the tumor is a more specific histology described by the term phenotype?

It appears that the first Other Sites applicable rule is H16 (and Table 2) instructing the use of histology code 8323 (mixed cell adenocarcinoma). However, this really is not an adenocarcinoma tumor but is a mixed squamous and transitional cell carcinoma. The 2018 ICD-O-3 Histology Update Table provides a new term for a but does not indicate whether that new term would also include a papillary squamotransitional cell carcinoma of the cervix.

An endometrial cancer was diagnosed in 2018. The endometrial biopsy showed malignant mixed mullerian tumor (MMMT/Carcinosarcoma). The total abdominal hysterectomy/bilateral salpingo-oophorectomy showed Endometrial Carcinosarcoma (50% serous carcinoma, 50% high grade sarcoma with rhabdomyoblastic differentiation) with invasion of 100% of the myometrium and involvement of the uterine serosa. I am not finding this in the Solid Tumor Rules or the site-specific ICD-O-3 code lists.

In Table 3 (Specific Histologies, NOS/ NST, and Subtypes/Variants), the entry for papillary carcinoma, NOS includes a change in column 3 of the 2018 Breast Solid Tumor Rules that conflicts with the H Rules. It is not accounted for in the change log. No explanation is offered as to why this change was made. This is a major change because encapsulated papillary carcinoma is frequently associated with carcinoma NST, and we have not been collecting these as such.

Encapsulated papillary carcinoma (8504) in column 3 now includes an indented entry, with invasive carcinoma, NST/invasive duct carcinoma 8504/3. However, most encapsulated papillary carcinomas are in situ or there is no definitive statement of invasive encapsulated papillary carcinoma, so when in situ and invasive tumors are present, we are instructed to code the invasive histology (which would be the invasive carcinoma (NST), 8500/3). How are registrars to arrive at the correct histology without a new H rule or a clarification regarding this update being documented in the change log?

Does the same change/addition apply to solid papillary carcinoma? These are often also associated with carcinoma, NST. Again, without an explanation regarding the change mentioned above, it is difficult to understand why the change was made.

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

For certain facilities in our area, the breast pathology reports using a CAP protocol format are formatted as follows; the Final Diagnosis will state Infiltrating carcinoma with the following features. The features list the specific tumor characteristics required in the CAP protocol formatting. The histology is always displayed in the list form and specified as Histologic type: (for example, Histologic type: Ductal carcinoma). Is this specific histology really to be ignored because it is preceded by the word type even if this is just a consequence of the pathology report formatting?

Rule H13 states to code the histology to metaplastic carcinoma when there is metaplastic carcinoma (or a subtype/variant) and invasive carcinoma NST. This rule makes no mention of lobular carcinoma. However, in Table 3, Note 2 for metaplastic carcinoma (8575) states metaplastic carcinoma, NOS and subtypes are almost always mixed with invasive mammary carcinoma, NST and at times lobular carcinoma. These tumors should be coded to metaplastic regardless of percent invasive mammary carcinoma or lobular carcinoma present.

While Table 2 (the mixed histology code table) does include an entry for metaplastic carcinoma AND carcinoma NST OR lobular carcinoma, it is unclear why lobular carcinoma has not been added to Rule H13 as well.

If a single tumor has metaplastic plus lobular carcinoma, Rule H13 does not apply and one has to continue through the rules. Unfortunately, the next rule registrars would be tempted to use is Rule H18: Code the histology that comprises greater than 50% of tumor when two histologies are on different rows in Table 3. This Rule does not state it does NOT apply to metaplastic carcinoma (only mucinous). So, if for some reason the lobular was greater than 50%, the incorrect histology would be coded (unless the registrar happened to remember Note 2 in the metaplastic carcinoma entry in Table 3).

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

Per the 2018 Solid Tumor Rules instructions, Final Diagnosis and Staging Summary (synoptic report) have equal coding priority. However, it is unclear which takes priority, or if this should be a combination of components, when the histologies are two different specific histologic types per Table 3 of the Breast Solid Tumor Rules Manual.

The 2018 Breast Solid Tumor Rules Equivalent Terms and Definitions - Changes from 2007 Multiple Primaries/Histology Rules states: Mammary carcinoma is a synonym for carcinoma no special type (NST)/duct carcinoma not otherwise specified (NOS) 8500. It will no longer be coded as carcinoma NOS 8010. Should metastatic carcinomas of breast origin be 8500, or is code 8010 (carcinoma NOS) more applicable because histology coding from metastatic sites is not as reliable?

In the April 2019 Breast Solid Tumor Rules update, the Priority Order for Using Documentation to Identify Histology was changed, giving equal priority to the Final diagnosis / synoptic report as required by CAP (item 2B).

There are technically two histologies documented for the case above; a Not Otherwise Stated (NOS)/No Special Type (NST) (invasive mammary carcinoma, per final diagnosis text) and subtype/variant (invasive cribriform carcinoma, per CAP report). If we do not use the synoptic report with priority over the final diagnosis, Rule H14 indicates the histology would be the NOS histology (invasive mammary carcinoma) because the percentage of tumor is not given for the subtype. However, SINQ 20180045 states, In the CAP protocol, the term Histologic Type is a label where the histology that corresponds to the largest carcinoma is collected. According to the CAP protocol for invasive breast cancer, the histologic type corresponds to the largest carcinoma.

If the pathologist summarizes the findings in a synoptic report, should the specific Histologic Type identified have priority?