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The ICD-O-3.2 Coding Table includes Mullerian mixed tumor as the preferred term for histology code 8950 (previously malignant mixed Mullerian tumor/MMMT). This table also includes carcinosarcoma, NOS as the preferred term for histology code 8980. Neither the ICD-O-3.2 Coding Table nor the Implementation Guidelines address the long-standing issue of coding histology for diagnoses of carcinosarcoma/malignant mixed Mullerian tumor.

These endometrial primaries are frequently diagnosed as both carcinosarcoma and MMMT. The questions regarding histology coding for carcinosarcoma and carcinosarcoma/MMMT of the endometrium date back to before the Multiple Primaries/Histology Rules, with at least three SINQ entries instructing registrars not to use code 8950/3 (MMMT) for diagnoses of MMMT. SINQ has instructed registrars that MMMT is a synonym for carcinosarcoma and these tumors should be coded to 8980 (carcinosarcoma), not to 8950 (MMMT). The most recent SINQ is partly inconsistent with the others, indicating 8950 can be used if the tumor is only described as MMMT. The other SINQ entries state carcinosarcoma should be used as it is the preferred term for MMMT. (See SINQ 20061008, 20100009, 20180071.)

The most recent SINQ (20180071) specifically indicates: According to the WHO Classification of Tumors of Female Reproductive Organs, 4th edition, MMMT (8950/3) is now a synonym for carcinosarcoma (8980/3) even though it has a separate ICD-O code. The ICD-O code for MMMT is no longer in the WHO book. However, MMMT is in the ICD-O-3.2 Coding Table and is not stated to be obsolete or a synonym. Which is correct, the clarification in the SINQ or the 2021 ICD-O-3.2 Coding Table?

For a 2021 diagnosis of carcinosarcoma/malignant mixed Mullerian tumor, how should registrars code the histology? Follow the previous SINQ entries and Rule H17 to code the histology to 8980 when the diagnosis includes both carcinosarcoma and MMMT? Do these previous SINQ entries still apply to cases diagnosed 2021 and later?

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

Recognizing the addition of the behavior requirement into this rule is an attempt to stop non-synchronous ductal carcinoma and lobular carcinomas from being accessioned as a single primary (SINQ 20200022), the issue with using behavior rather than timing is that now, synchronous separate/non-contiguous tumors that are invasive carcinoma NST (8500/3) and lobular carcinoma in situ (8520/2) (or vice versa) are separate primaries per M14.

Lobular and carcinoma, NST are separate rows in Table 3, so we cannot stop at M10 and code the mixed histology because there are two separate histologies with different behaviors. There is no rule that states we can just ignore the in situ tumors for the purpose of applying the M Rules. (We are instructed to ignore the in situ when coding histology only in certain circumstances.) The problem with Rule M10 appears to be related to timing.

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

Patient has a resection labeled as: Spine, designated intramedullary lesion. The Final Diagnosis is: Melanocytic neoplasm with features most consistent with primary intramedullary melanocytoma. The Diagnosis Comment states: The overall immunophenotypic and morphologic impression is a primary central nervous system melanocytoma.

The ICD-O-3 lists melanocytoma, NOS histology code as 8726/0, but does not provide a site-associated code. If the ICD-O-3 is used, the histology would be 8726/0 and the primary site presumably would be C720 since the tumor was specifically described as being intramedullary (i.e., within the spinal cord medulla).

Table 6 (Solid Tumor Rules, Non-Malignant CNS Equivalent Terms and Definitions) does not list either an intramedullary melanocytoma or melanocytoma (NOS). However, Table 6 does include meningeal melanocytosis 8728/0 and meningeal melanocytoma 8728/1. If Table 6 is used and the histology is coded 8728/1, then the primary site would presumably be C701 per the ICD-O-3 site-associated listing for this histology (C709).

Per Mayo consulting pathologist, the final diagnosis on this right lung biopsy is: SMARCA4-deficient malignant neoplasm (see Comment). Comment: Sections show a poorly-differentiated malignant neoplasm without any apparent glandular, squamous, or stromal differentiation. The tumor near totally replaces the underlying lung tissue without recognizable underlying alveolar parenchyma. Immunohistochemical stains performed at Mayo Clinic (Oscar keratin, INSM1, NUT, S100, desmin and BRG1 protein encoded by SMARCA4 gene) demonstrate that the malignant cells are positive for Oscar keratin (rare cells only), synaptophysin (weak/patchy) and p63 (focal) while negative for the remaining antibodies tested. Of note, SMARCA4 stain is negative in the tumor cells. Thus, this tumor can be categorized as a SMARCA4-deficient malignant neoplasm, which is known to be an aggressive malignancy, likely represent a SMARCA4-deficient thoracic sarcoma, a recently described entity. SMARCA4-deficient carcinomas in the lung have been reported to be mostly adenocarcinomas or squamous cell carcinomas, which would not fit for this case. Please refer to a paper published by our group (Sauter JL et al. Mod Pathol 2017;30:1422-32.

The radiologist noted the mass was most compatible with a chondroid lesion, which is not reportable on its own, but can the subsequent term be used to accession this as reportable if only one malignant etiology is provided by the radiologist? Or does the statement imply that this is only one of several possible etiologies?

SINQ 20200022 indicates that cases originally diagnosed as in situ do not have a new primary when a new invasive tumor with a different histology is diagnosed within 5 years. Should histology and/or behavior get updated for the in situ breast primary?

Lung Rule M14 appears to be the first rule that applies to this case and instructs the user to abstract a single primary. However, we were hoping for confirmation that a cancer (NOS) or malignancy (NOS) would not be a distinctly different histology that may qualify for Lung Rule M8. Currently, these histologic terms are not included in the Table 3 options or mentioned in the preceding notes.

A patient had posterior cervical lymphadenopathy status post biopsy and subsequent lymph node dissection showed metastatic melanoma in 2018. Workup showed no skin lesions or primary site. Final diagnosis is melanoma of unknown primary (unknown if cutaneous or non-cutaneous). Should C760 be used as the primary site for this case since the histology codes of 8700-8790 are included in the Cervical Lymph Nodes and Unknown Primary Tumors of the Head and Neck schema in SEER*RSA?

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 ICD-O-3.2 Implementation Guidelines and ICD-O-3.2 Coding Table indicate that insulinoma, NOS has changed behavior from /0 to /3 for cases diagnosed 2021 and later. However, the ICD-O-3.2 Implementation Guidelines do not indicate whether this change applies to tumors described as above. Insulinomas are generally neuroendocrine tumors/neoplasms, so it seems any neuroendocrine tumor described as an insulinoma should be collected as 8151/3, but does that apply to an epithelioid tumor/neoplasm also described as insulinoma?

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