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Patient had a breast excision that proved a single tumor with no evidence of invasive carcinoma. The final diagnosis stated: Size (extent) of EPC DCIS: Spanning approximately 1.3 cm. The pathologist did not describe separate foci of DCIS; only one tumor comprised of both encapsulated papillary carcinoma and DCIS. The encapsulated papillary carcinoma was not described as invasive. The pathology noted: This case is best classified as EPC conventional DCIS. No conventional stromal invasion is identified. Solid Tumor Rule M2 confirms a single tumor is a single primary.

However, there does not appear to be an H Rule that instructs how to code histology. The Single Tumor: In Situ Only module, has only three H Rules and none of them apply to this case. The patient does not have Paget disease (H1), does not have a single histology (H2, there are multiple histologies present as DCIS and EPC are listed on different rows in Table 3) and does not have DCIS and LCIS (H3). How does one arrive at the correct histology for this case?

Table 6 (Tumors of the Oropharynx, Base of Tongue, Tonsils, Adenoids) in the Head and Neck Equivalent Terms and Definitions lists both squamous cell carcinoma HPV-positive and squamous cell carcinoma HPV-negative as subtypes/variants of squamous cell carcinoma (the NOS histology, 8070). Squamous cell carcinoma HPV-positive and squamous cell carcinoma HPV-negative are also listed in the 2018 ICD-O-3 update table.

Previous clarification from the standard setters regarding the 2018 ICD-O-3 Update table indicated that histology codes 8085 and 8086 (HPV-positive and HPV-negative squamous cell carcinoma, respectively) included p16+ and p16- squamous cell carcinoma, respectively. Presumably, this clarification was made because p16 is a surrogate marker for HPV, and capturing whether a tumor is HPV-related or not has implications for staging for 2018 and later diagnoses. However, this clarification was not added to the 2018 ICD-O-3 Update table via errata, nor do the Head and Neck Equivalent Terms and Definitions or Histology Coding Rules address this.

Is a diagnosis of p16-positive squamous cell carcinoma equivalent to a diagnosis of squamous cell carcinoma HPV-positive (8085)? If so, will this clarification be added to the Head and Neck Solid Tumor Rules?

Cytology is not listed in the Priority Order for Using Documentation to Identify Histology (Histology Coding Rules) in the Head and Neck schema. Other schemas do include cytology in the hierarchy below tissue from a biopsy or resection. Cytology is often less specific than histology, so one would expect cytology to be listed below tissue in this hierarchy. Was this an oversight? Or would cytology be equivalent to histology if it provided the most specific histology for the case?

Glioblastoma multiforme is listed as a synonym for the preferred term glioblastoma, NOS (9440) per Table 3 Column 2. Therefore, it seems reasonable to assume that a diagnosis of glioblastoma, NOS would be a new primary if it followed a glial or astrocytic tumor. However, in general, the Solid Tumor Rules use the preferred terminology and/or indicate when a specific rule also includes any tumor diagnosed as a subtype/variant. Rule M6 does not explicitly include a diagnosis of glioblastoma, NOS or any of its subtypes/variants (e.g., glioblastoma IDH-mutant or gliosarcoma). Does Rule M6 apply to any diagnosis of glioblastoma, NOS and any of its synonyms or subtypes/variants?

An endometrial cancer was diagnosed in 2018. The endometrial biopsy showed malignant mixed mullerian tumor (MMMT/Carcinosarcoma). The total abdominal hysterectomy/bilateral salpingo-oophorectomy showed Endometrial Carcinosarcoma (50% serous carcinoma, 50% high grade sarcoma with rhabdomyoblastic differentiation) with invasion of 100% of the myometrium and involvement of the uterine serosa. I am not finding this in the Solid Tumor Rules or the site-specific ICD-O-3 code lists.

Similar to an issue previously submitted SINQ 20180063, Table 1 (WHO Grades of Select CNS Neoplasms) in the Non-Malignant CNS Equivalent Terms and Definitions section states WHO Grade I tumors are always non-malignant. However, this does not mean that the tumors listed in Table 1 as WHO Grade I are always benign (/0). Some tumors listed with a WHO Grade I have a behavior of /1 (borderline) per the ICD-O-3 and/or Tables 5 and 6. The Behavior coding instructions do not currently indicate these are the appropriate sources to use when the pathologist and/or physician do not comment on the behavior of these tumors. In our area, pathologists do not explicitly state the behavior for these tumors; the pathologist only assigns the WHO Grade.

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?

A patient has a left breast cancer diagnosed in 2011; then has a "recurrence" in her lymph nodes in 2017. In 2018, she has a new left breast mass that is the same histology and behavior as the 2011 cancer. Based on the 2017 "recurrence" in the lymph nodes, this is not a new breast primary, is that correct?