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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.

Penile mass excision shows final diagnosis of squamous cell carcinoma, verrucous type. Subsequent partial penectomy has a final diagnosis of squamous cell carcinoma, verrucous type and the summary cancer data lists

Both the final diagnosis and summary cancer data indicate a histology code of 8051/3 (squamous cell carcinoma, verrucous type / verrucous carcinoma). However, this site and histology combination triggers edit IFN4911. Edit documentation indicates that for sites C600-C609 (all penile sites) use histology code 8051 and do not use 8054.

Review of the 2018 ICD-O-3 Histology Updates table does not indicate these terms are synonymous.

Bone marrow, right iliac crest (aspirate smear, touch preparation, clot section and core biopsy): Hypercellular marrow (40-50%) with plasma cell neoplasm (see Comment): " No evidence of metastatic carcinoma. " Adequate iron storage.

Comment: CBC data shows normocytic anemia. Flow cytometric analysis of bone marrow detects a kappa restricted plasma cell population that expresses CD138 and CD38. CD56 is positive. CD19 and CD20 are negative. T lymphocytes are immunophenotypically unremarkable. Polyclonal B lymphocytes are detected. Blast gate is not significantly increased. Immunohistochemical stains are performed on the biopsy core and clot section for greater sensitivity and further architectural assessment with adequate controls. CD138 positive plasma cells comprise > 70% of the total cellularity. AE1/AE3 is negative. Taken together, the morphologic and immunophenotypic findings are consistent with a diagnosis of plasma cell neoplasm. Trilineage hematopoietic activity as are seen.

It is unclear if code 300 is appropriate, since technically the fissure is comprised of pleura, involvement of the fissure appears to imply a tumor that is no longer localized.

An argument could be made for code 400, since the term traverses could be interpreted as crossing into adjacent lobe, however the lower lobe is not mentioned in this scan.

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?

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.

Example 1: 5/2013 diagnosis of HCC in segment 4B (single tumor), treated with microwave ablation in 7/2013. CT scan in 11/2017 with new 23mm hypodensity in liver segment 4 suspicious for recurrent disease. Clinical assessment in 1/2018: New enlarging lesion in liver most consistent with progression of HCC. Treated with RFA in 2/2018. Is the 2018 occurrence a new primary as imaging stated this was a new lesion?

Example 2: 7/2017 diagnosis of HCC in right liver; 2.5 cm lesion in segment 5/6 with a couple of satellites and 12mm lesion in segment 6, treated with Y90 radioembolization. Follow-up note in 11/2017: complete response of treated cluster of lesions in segment 5/6 and lesion in segment 6, increase in size of caudate lesion not amenable for treatment (this lesion was stated to be indeterminate on 7/2017 imaging). Caudate lesion finally stated as LI-RADS5 on 3/2018 imaging and was treated with chemoembolization 6/2018. 7/2018 and 10/2018 Follow-up imaging states LR-TR nonviable lesion in caudate lobe. 8/2019 CT shows caudate lobe with arterial enhancement, new compared to prior imaging, LR-TR viable. MD note states patient has small local HCC recurrence in segment 1 (caudate lobe) with plan to repeat TACE. Is this 8/2019 HCC a new primary as the patient was disease free for greater than 1 year, or is it the same tumor and a single primary?

11/18/2019 Left 1st Digit/Thumb Biopsy: Atypical Melanocytic Proliferation consistent with Early Acral Lentiginous Melanoma in situ. Margins Positive. (Not a reportable diagnosis for 2019.)

12/5/2019 Left 1st Digit Shave Biopsies: Malignant Melanoma in situ. Margins Positive.

1/15/2020 Started Aldara (treatment plan: use for ~3 months then Mohs/excision, but due to COVID could not get resection until 7/2020).

7/29/2020 Left Thumb Excision: Residual Melanoma in situ. Margins Positive. Treatment Plan: re-excision.

8/6/2020 Left Thumb Re-Excision: Atypical Lentiginous Melanocytic Proliferation at the 12-2 margin may represent the advancing edge of melanoma in situ. (8/19/2020 Plan to treat the 12-2 margin as positive with in situ; plan for re-excision).

8/20/2020 Left Thumb Re-Excision & Left Nail Plate Excision: Malignant Acral Lentiginous Melanoma with extensive melanoma in situ. Breslow 1.3mm. Margins Positive. Nail plate & bed epithelium with hemorrhage and a mild increase in melanocyte density likely represent melanoma in situ.

9/4/2020 Left thumb partial amputation & Left axillary Sentinel Lymph Node Excision: Residual Malignant Melanoma in situ. 0/3 sentinel nodes positive.