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Table 19: Vulva Histologies of the Other Sites Solid Tumor Rules does not include entries for either keratinizing or nonkeratinizing squamous cell carcinoma in the “Squamous cell carcinoma, NOS” row. However, these are two distinctly different histologies per the ICD-O-3.2.

All other Solid Tumor Rules schemas include an M Rule instructing one to abstract multiple primaries when separate/non-contiguous tumors are two or more different subtypes/variants in Column 3 of the Specific Histologies, NOS, and Subtype/Variants Table for the schema (e.g., Rule M6 for Lung). The timing of these tumors is stated to be irrelevant. The Notes confirm the tumors may be subtypes/variants of the same or different NOS histologies and tumors in column 3 are all distinctly different histologies (even if they are in the same row). However, the 2023 Other Sites schema appears to be missing this rule.

Should these distinctly different histologies be accessioned as separate primaries? Is an M Rule missing from the Other Sites schema to address distinctly different histologies?

Patient had a mandibular mucosal lesion resected in June of 2023, with a diagnosis of “atypical squamous proliferation” and case was forwarded to an expert in oral pathology for best classification. Subsequent slide review final diagnosis was “moderate to severe squamous dysplasia.” That slide review diagnosis goes on to state “microscopic focus suspicious for superficial invasion.”

Currently there is no ICD-O code for severe squamous dysplasia, however it is unclear if this terminology is equivalent to high grade squamous dysplasia (histology code 8077/2).

The 10/2023 TURBT final diagnosis is “Urothelial carcinoma with mixed histologic appearances, see synoptic summary below for details.” The synoptic report includes, “Histologic Type Comment: Invasive carcinoma percentages: Micropapillary 60-70%, high grade or poorly differentiated urothelial 20-30%, squamous 10-20%.” The squamous component is stated to be “Urothelial carcinoma with squamous differentiation.”

It appears there are two specific urothelial carcinoma subtypes to consider: Urothelial carcinoma, micropapillary variant (8131/3) and poorly differentiated carcinoma (8020/3). The squamous component would not be considered because there is no specific histology for “squamous differentiation.”

The micropapillary component is the predominant histology (60-70%) in this case, and it does seem like this is important to capture. However, the WHO Blue Book indicates poorly differentiated carcinoma of the bladder has a poor prognosis.

There was a 3.5 cm invasive adenocarcinoma tumor in the pancreatic head. There were four separate, sized pancreatic neuroendocrine tumors measuring 0.9, 0.7, 0.5 and 0.2 cm in the pancreatic body. There are multiple tumors with distinctly different histologies. However, Table 11 (Pancreas Histologies) does not include any entries for neuroendocrine tumors of the pancreas (e.g., pancreatic NET, WHO grade 1, histology 8240). While it would seem Rule M19 should apply as they’re distinctly different histologies, because PanNETs are not included in Table 11, it is not clear which M Rule applies to these multiple tumors.

If Rule M19 does not apply, we are left with Rule M21 (Abstract a single primary when there are multiple tumors that do not meet any of the above criteria). Are these separate tumors with distinctly different histologies really a single primary? Pancreatic neuroendocrine tumors are not an uncommon histology, is there a reason these were not included in Table 11?

The patient was not synchronously diagnosed with multiple tumors, but three separate tumors with three different histologies were diagnosed at different times and no more specific histology was provided for the NSCLC. The timing rules do not apply to this case (the tumors were not greater than 3 years apart and they were not synchronously/simultaneously diagnosed).

While NSCLC is a NOS histology for both adenocarcinoma and squamous cell carcinoma, it is unclear if Rule M8 should apply because NSCLC is not listed in Table 3 (Table 3 is not an exhaustive list). In some situations, Rule M8 would apply if the tumors were different histologies and one of the histologies was not listed in the Table. Does that logic still apply if one of the tumors is NSCLC? If NSCLC is excluded from Rule M8, is Rule M14 the appropriate M Rule for the 2022 NSCLC diagnosis?

This patient does not have a previous diagnosis of prostate adenocarcinoma nor a previous history of androgen-deprivation therapy.

Does the logic in the Other Sites Solid Tumor Rules (STRs) noted in SINQ 20200052 still apply? This SINQ confirms a diagnosis of mixed prostatic adenocarcinoma and small cell neuroendocrine carcinoma is 8045. This matches the STRs instructions for Rule H21 and Table 2 (Mixed and Combination Codes), row 1. Row 1 indicates a mixed small cell carcinoma and adenocarcinoma is combined small cell carcinoma (8045). For a patient without previous treatment, is this the correct mixed histology code?

SINQs 20190083, 20180088, and 20130221 all indicate diagnoses of prostate adenocarcinoma, followed by a diagnosis of metastatic small cell carcinoma of the prostate are separate primaries because these are distinctly different histologies. Does this logic still apply for 2023 and later since Rule M4 was added to the Other Sites M Rules? Rule M4 states, “Abstract multiple primaries when the patient has a subsequent small cell carcinoma of the prostate more than 1 year following a diagnosis of acinar adenocarcinoma and/or subtype/variant of acinar adenocarcinoma of prostate.”

This patient has a 2018 diagnosis of prostate adenocarcinoma treated with radical prostatectomy, followed by a 2023 diagnosis of metastatic small cell carcinoma of the prostate diagnosed on a liver metastasis core biopsy. Rule M4 does not indicate whether it applies to subsequent biopsy confirmed metastatic tumor only. When a diagnosis of small cell carcinoma follows a diagnosis of prostatic adenocarcinoma, it is almost always confirmed in metastatic sites rather than in the primary site. Does the logic in the referenced SINQs above still apply for Rule M4?

The AJCC 8th edition confirms that the identification of psammomatous calcifications within a cervical lymph node is metastatic disease.

Example:  Patient had a thyroid lobectomy and level VI neck node excision in August 2022. The final diagnosis is multifocal papillary carcinoma of the thyroid, as well as rare psammomatous calcifications only in the resected node. The pathologist notes that “psammoma bodies only” in lymph nodes is not well defined, and while indolent, they do indicate capacity for lymphatic spread and are pN1a.

Should thyroid primaries with cervical node psammomatous calcifications get captured in EOD Regional Nodes category as it is in the AJCC pN staging?