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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?

Since the peripheral nerves are included in the Malignant CNS schema of the Solid Tumor Rules, neither the differences in subsite nor timing indicate these are separate primaries (Rule M10 indicates a single primary). However, these are separate MPNSTs in different sites and the tumors are not stated to be metastasis. Additionally, these are treated as separate primaries by the managing physician.

While the malignant CNS tumors do not take timing into account, is this correct for these peripheral nerve tumors that are often treated similarly to soft tissue tumors? Should Rule M8 be updated to include tumors in different peripheral nerve subsites?

2021-Right pleural fluid:  Negative for carcinoma.

5/18/2021: Right iliac crest bone marrow core biopsy, aspirate smear, clot section and peripheral blood smear:  Hypercellular bone marrow, morphological findings are suspicious for a myeloproliferative neoplasm. Flow Cytometry: Slight immunophenotypic abnormalities of the myeloid cells. No abnormal B cell, T cell, or NK cell populations identified. Normal female karyotype. KARYOTYPE: 46,XX[20]. Negative for deletion of 13q14.3 (D13S319) by FISH. Negative for deletion of 13q34 (LAMP1) by FISH. Negative for hyperdiploidy involving chromosome 9 by FISH. Negative for t(9;22)(q34;q11.2) by FISH. Negative for deletion of the EGR1 gene on 5q31 by FISH. Negative for monosomy 5 by FISH. Negative for deletion of 7q31 by FISH. Negative for monosomy 7 by FISH. Negative for deletion of 20q12 by FISH. Negative for trisomy of chromosome 8 by FISH.

6/4/21-Left adrenal; biopsy: poorly-differentiated malignant neoplasm with extensive necrosis. Immunohistochemical stains show the neoplastic cells to be negative for CK7, TTF-1 and p63. Negative CK7 and TTF-1 would argue against a lung primary. Correlation with clinical and radiological findings is advised.

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Example:  A prostate core biopsy showed intraductal carcinoma in 09/2022, which is an in situ tumor.  A core biopsy again showed intraductal carcinoma in 12/2022.  The subsequent radical prostatectomy in 04/2023, revealed multiple foci of invasive prostate adenocarcinoma with extensive intraductal carcinoma. 

Per Solid Tumor Rules, Other Sites, Rule M3, acinar adenocarcinoma of the prostate is always a single primary.  Note 4, this rule applies to subtype variants of acinar adenocarcinoma listed in Table 3, which has intraductal/ductal as a variant subtype of acinar adenocarcinoma. Does rule M3 apply to incidence cases (an invasive tumor following an in situ tumor)?

The 2023 SEER Manual indicates PRRT should be coded in the Other Therapy field per coding instruction 2.d.  Likewise, SINQ 20180106 instructs to code PRRT as Other Therapy, while the discussion portion clearly outlines the radioactive nature of this modality.

Would PRRT be best coded as a radioisotope in the Radiation Treatment Modality--Phase I, II, III field rather than in the Other Therapy field?

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).

In 2021, the patient was diagnosed with a non-reportable appendiceal LAMN.  Resection showed a tumor diffusely involving the appendix and perforating the visceral peritoneum, as well as extensive intraperitoneal metastasis.  In 2023, a lung wedge resection revealed metastatic mucinous neoplasm involving lung parenchyma and pleura, consistent with metastasis of the known appendiceal primary.  It is understood that intraperitoneal spread of an appendiceal LAMN does not make it reportable because the peritoneal disease is also non-invasive.  Does extraperitoneal metastasis of an appendiceal LAMN diagnosed prior to 2022 make it invasive disease and therefore reportable? 

The resection pathology report final diagnosis indicates this is both mixed mucinous and non-mucinous with a lepidic predominant component. The pathologist notes this is “Lepidic: 75%. Acinar: 25%.”  The percentage of the mucinous component is not documented.

Rule H1, Note 1, states “When mucinous carcinoma is mixed with another histology, such as adenocarcinoma and mucinous carcinoma, code mucinous ONLY when mucinous is documented to be greater than 50% of the tumor.” While mixed invasive mucinous and non-mucinous carcinoma is included in Table 2 (Combination/Mixed Histology Codes) without a required percentage, it is unclear whether one should move past Rule H7 and use Rule H8 to code this combination histology code. Rule H7 would instruct one to code the histology to lepidic adenocarcinoma (adenocarcinoma, lepidic predominant) based on the percentage of the lepidic component in the tumor. However, this does not address the mixed mucinous and non-mucinous diagnosis. Which H Rule and histology apply to this case?

Patient had a total abdominal hysterectomy-bilateral salpingo-oophorectomy performed in January 2023 with final diagnosis of myxoid and epithelioid leiomyosarcoma.

Diagnosis comment states: The tumor is 15 cm per report. It grows in nests and poorly formed interanastomosing trabeculae and cords that are separated by abundant myxoid background. The cells have an epithelioid morphology with eosinophilic cytoplasm, large nuclei, and very prominent nucleoli. The mitotic activity is overall low ranging from 1 to 3/10 HPFs.

Immunohistochemical stains performed at the outside hospital showed diffuse positivity for SMA, desmin, caldesmon, and PR. They are negative for CD10, claudin-4, calretinin, HBM45, MART1 (rare weakly positive cells), PANCK, and SOX10. This immunohistochemical profile supports a smooth muscle derivation of this neoplasm. As this tumor is extensively myxoid, diagnostic criteria differ from the spindle cell leiomyosarcoma.

Per Solid Tumor Rules Other Sites, Table 16: Uterine Corpus Histologies, Epithelioid Leiomyosarcoma (8891/3) and Myxoid Leiomyosarcoma (8896/3) are both subtypes of Sarcoma, NOS (8800/3).  Per Rule H21, use a combination code when there are multiple specific histologies AND the combination is listed in Table 2 OR there are coding instructions for the combination in the applicable histology Tables 3-21 OR you receive a combination code from Ask A SEER Registrar.  Since there is no combination listed in Table 2 and there is no instruction for the combination in Table 16, how should the histology be coded for this tumor?