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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.

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.

The 2021 ICD-O-3.2 Update includes papillary microcarcinoma (8341/3) as the preferred term for thyroid primaries (C739). However, there are multiple SINQ entries instructing registrars not to use code 8341/3 for diagnoses of micropapillary carcinoma of the thyroid (including SINQ 20071076, 20081127, 20110027, 20150023, and 20180008).

SINQ 20150023 specifically indicates: Per the WHO Tumors of Endocrine Organs, for thyroid primaries/cancer only, the term micropapillary does not refer to a specific histologic type. It means that the papillary portion of the tumor is minimal or occult (1 cm or less in diameter) and was found incidentally. WHO does not recognize the code 8341 and classifies papillary microcarcinoma of the thyroid as a variant of papillary thyroid carcinoma and codes histology to 8260. If the primary is thyroid and the pathology states papillary microcarcinoma or micropapillary carcinoma, code 8260 is correct.

Does this clarification apply to cases diagnosed 2021 and later? If WHO feels the term micropapillary still does not refer to a specific histologic type for the thyroid, why is 8341/3 listed as a preferred term for this morphology/site combination? For cases 2021 and later, should a diagnosis of Incidental papillary thyroid microcarcinoma (3 mm) in left lower pole, be coded as 8341/3 per the ICD-O-3.2, or as 8260/3 per clarification in multiple SINQ entries?

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

According to the literature, PMH is a low-grade malignant vascular neoplasm of different tissue planes including skin and soft tissue. However, the references also state: PMH is a cutaneous tumor that behaves in an indolent fashion. There is no indication that this was a malignant diagnosis.

12/3/18 Foot, left skin lesion, punch biopsy: Superficial squamous epithelium demonstrating hyperkeratosis and fragments of keratin debris, no tumor seen.

Foot, left skin lesion, punch biopsy: Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma, see note.

NOTE: The submitted immunohistochemical slides were reviewed. Positive and negative controls reacted appropriately. The tumor cells demonstrate immunoreactivity to CK AE1/AE3 and CK7. The CD31 immunoreactivity described in the report cannot be confirmed as only the positive control is submitted for review. The tumor cells are negative for desmin, CD45, CD68, S-100, CD34, SMA, CD20, and HHV8. The proliferative index via Ki-67 is approximately 10%. The morphology (described below) and immunohistochemistry performed are compatible with a pseudomyogenic hemangioendothelioma.

12/4/18 Final Pathologic Diagnosis: Foot, left bone lesion, biopsy: Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma, see note.

Note: The patient's imaging findings were reviewed in conjunction with this case, revealing numerous lytic lesions of the tibia, fibula, talus, tarsal, metatarsal, and phalangeal bones. Additionally, as per the medical record, also reviewed in conjunction with this case, there are lesions of the skin. Thus, an extensive immunohistochemical panel was performed in an attempt to support the morphologic findings in this case, which were morphologically similar to the patient's skin biopsy. The tumor cells demonstrate strong immunoreactivity to pancytokeratin (CK AE1/AE3) and vimentin with moderate immunoreactivity to Fli-1. The tumor cells demonstrate weak immunoreactivity to epithelial membrane antigen. INI-1 is retained. There is focal immunoreactivity to CD31 although this is limited to the edges of the tissue fragments. The tumor cells are negative for HHV-8, CD34, smooth muscle actin, CK8/18, desmin, CD99, and Bcl-2. The combination of morphologic (see below for microscopic description) and immunohistochemical findings are consistent with pseudomyogenic hemangioendothelioma. Fresh tissue was submitted for karyotype analysis at the time of intraoperative consultation; however, it revealed only a normal appearing male karyotype. Thus, molecular confirmation was sought. The original slides and a paraffin block were submitted for FOSB rearrangement analysis, as pseudomyogenic hemangioendothelioma is known to have recurrent rearrangements with FOSB. Additional immunohistochemistry performed at (FACILITY) demonstrating immunoreactivity for ERG, supporting a vascular origin for this neoplasm. Fluorescence in situ hybridization demonstrated that 13% of the cells examined show FOSB rearrangement. While this FISH probe is for investigational purposes, the above findings support the diagnosis of pseudomyogenic hemangioendothelioma.

Scenario: Patient had a transurethral resection of the prostate on 8-29-19, positive for basal cell carcinoma with focal squamous differentiation involving approximately 50% of tissue (determined not to be mets by consult). On 11-14-19, the patient had a prostatectomy positive for residual basal cell carcinoma and a small focus of infiltrating prostatic adenocarcinoma. According to AJCC, 8th edition, page 724, basal cell carcinoma of the prostate is 8147/3 and we ignored the small focus of adenocarcinoma. The above scenario was reported as two primaries (8090/3 and 8140/3), but we are thinking it is one.

Rule H6 states: Code 8742/3 (Lentigo maligna melanoma) when the diagnosis is lentigo maligna melanoma with no other histologic types. However, if the diagnosis was strictly lentigo maligna or lentigo maligna melanoma, the first rule that applies is Rule H1 because lentigo maligna melanoma is a single, specific histologic type and Rule H1 states, Code the histology when only one histologic type is identified. Following the current rules, one would never arrive at Rule H6. Should the H Rules be reordered? Or should an example of when one would use Rule H6 be added to clarify when to use this rule?

Patient is diagnosed July 2021 with high-grade serous carcinoma on ascites cytology. Tumor debulking total abdominal hysterectomy/bilateral salpingo-oophorectomy in August shows high-grade serous carcinoma involving the right ovary (capsule intact, right fallopian tube is negative), left ovary (capsule ruptured), and fallopian tube. Pathologist has chosen tumor site to be bilateral ovaries in the staging summary, with the left fallopian tube listed as “other tissue/organ involvement” along with uterus, peritoneum, and omentum. Additional findings in staging summary includes serous tubal intraepithelial carcinoma (STIC).

Our interpretation of SINQ 20210025 is that any case with both ovarian and tubal involvement would be coded as a fallopian tube primary if STIC is present, even when the pathologist is clearly calling the case ovarian. If this is correct, then the previous SINQ 20120093 may need to be updated with a date restriction reference since it would be in disagreement with this instruction.

If our interpretation is incorrect, then the STIC would be an additional primary per MP/H Rule M11.

Patient has a history of B-cell lymphoma with multimodality treatment in 2002. Lab work in 2015 showed multilineage dysplasia leading to a diagnosis of therapy-related myelodysplastic syndrome. Patient presents in 2020 for a bone marrow biopsy now showing low-grade MDS. The MDS appears to have the same multilineage dysplasia previously identified.

MDS, NOS is not listed in the Heme DB as a possible transformation of t-MDS, nor is it listed as a Same Primary for t-MDS. Likewise, t-MDS is not listed as a more specific myelodysplastic syndrome, a transformation of MDS NOS, or a Same Primary as MDS, NOS.

The first M rule that applies to this case is M15, and the Multiple Primaries Calculator indicates that the MDS, NOS should be a new primary.