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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.

The Histology Coding Instructions give priority to the Final Diagnosis over the CAP protocol. However, when pathology reports are formatted using the CAP protocol, the presence of in situ carcinoma is generally only mentioned in the CAP protocol. Can the presence of in situ tumor mentioned only in the CAP protocol be used to apply rule H7 (Single Tumor: Invasive and In Situ Components Module)? Or are the rules in the Single Tumor: Invasive Only module used?

Example: Final diagnosis is invasive ductal carcinoma. CAP protocol mentions,

The Heme DB originally stated the Definitive Diagnostic Method is coded to 8 [clinical diagnosis only] while an updated version stated it can coded as a clinical diagnosis or it can be based on the results of a bone marrow biopsy or a genetic test. The Abstractor Note section specifies this is a diagnosis of exclusion. According to a recent Web-based training seminar, the JAK-2 diagnosis would be coded 5 [positive laboratory test/marker study]. Doesn't the Definitive Diagnostic Method of a clinical diagnosis/diagnosis of exclusion mean that the diagnostic confirmation of essential thrombocythemia will always be coded as 8 [clinical diagnosis only]? Many people use code 3 for positive bone marrow biopsy and genetics (JAK-2), but the bone marrow is usually reported as only borderline or is stated to be abnormal for a person's age.

The Heme DB identifies these as new primaries:

10/12/12 Large intestine, biopsy: Diffuse large B-cell lymphoma.

10/12/12 Bone marrow biopsy: Peripheral T-cell lymphoma.

The Hematopoietic and Lymphoid Neoplasms Database (Heme DB) definition for systemic mastocytosis with an associated hematological neoplasm (SM-AHN, 9741/3) states SM-AHN is a variant of systemic mastocytosis that arises with a myeloid disease of non-mast cell lineage (e.g., MDS, MPN, etc.) and that,

However, SINQ 20130172 conflicts with the Heme DB stating the systemic mastocytosis and the associated hematological neoplasm are a single primary coded to a single histology (9741/3) per Rule M2.

The FORDS Manual (pg. 22) states: The first course of treatment includes all methods of treatment recorded in the treatment plan and administered to the patient before disease progression or recurrence. The instructions in the FORDS Manual and clarification from multiple CAnswer Forum posts indicates the planned first course treatment stops following disease progression, even when the first course treatment plan is not altered or changed.

SEER, on the other hand, instructs registrars to do the opposite. The SEER Manual instructs registrars to code all completed treatment given as part of the initial first course treatment plan, even after disease progression, provided the treatment plan is not changed or altered. (See 2016 SEER Manual, Section VII First Course of Therapy, Treatment Timing, Rule 1 and Example 1.)

For consistency in data collection, shouldnt the standard setters use the same guidelines to define first course treatment? Given that the majority of cases are reported to SEER by registrars in CoC facilities, who may not be abstracting treatment modalities that occur after progression, the SEER expectation is likely not able to be performed consistently. Wont this difference in standard setter data collection expectations negatively impact the treatment data reflected on our files?

The FNA showed high grade B-cell lymphoma, morphologically compatible with diffuse large B cell lymphoma. Special studies state: Tumor cells are positive for Vimentin, CD45, and CD20, focally weakly positive for CD43; negative for Myeloperoxidase, CD99, AE1/AE3, CK7, CK20, S100, CD3, cyclin D1, CD34, CD5 and TTF1. The cellular findings and immunophenotype are compatible with large B-cell lymphoma.

The treating physician refers to this disease process and is treating the patient for diffuse large B-cell lymphoma. Should the histology be coded as B-cell lymphoma, NOS (9591/3) because both the FNA and the immunophenotyping use ambiguous terminology? Does the physician reference to the disease process as diffuse large B-cell lymphoma, Stage II-AE impact the histology used?

The Extent of Disease (EOD) manual states that "Confined to thymus WITH mediastinal or pleural involvement" should be coded as regional by direct extension. I have EOD primary tumor coded as 200 and based on SEER*RSA, this is localized.

The Extent of Disease (EOD) Manual states: Neoadjuvant (preoperative) therapy: If the patient receives neoadjuvant (preoperative) systemic therapy (chemotherapy, immunotherapy) or radiation therapy, code the clinical information if that is the farthest extension documented. If the post-neoadjuvant surgery shows more extensive disease, code the extension based on the post-neoadjuvant information.

The Equivalent Terms and Definitions sections in the Solid Tumor Rules for these schemas identify which sites must have laterality coded, but there is no instruction for coding laterality when bilateral tumors are a single primary. The SEER Manual currently only indicates code 4 (bilateral) is seldom used (e.g., bilateral ovarian tumors, Wilms tumors, etc.) but does not indicate laterality code 4 should be used for CNS tumors. Is this note going to be updated or should a non-bilateral code be applied?

Example: MRI demonstrates multiple left-sided dural-based meningiomas including a 4.4 cm left posterior fossa meningioma, a 0.8 cm left frontal-parietal meningioma and a right posterior frontal meningioma. The large left posterior fossa meningioma was resected and proved atypical meningioma. Should the laterality be 4 (bilateral) as the patient had both left and right-sided meningiomas confirmed to be a single primary? Or should the laterality be coded as 2 (left) since only the large left-sided meningioma was proven to be a borderline tumor (atypical meningioma, 9539/1) and the others were benign?