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1) In the SEER Manual's code definitions for Neoadjuvant Therapy - Treatment Effect, some sites specify the percentage of viable tumor. Pathology reports often list this along with the percentage of necrosis (e.g., 10% necrosis and 90% viable tumor). If only the percent necrosis is stated, is it acceptable to infer the percent viable tumor? For example, pathology report states only "treatment effect: present, necrosis extent: 30%" - could we then deduce that the percent viable tumor in this case would be 70%?

2) Can statements of Residual Cancer Burden (RCB) Class be used?  For example, pathology report states Treatment Effect: Residual Cancer Burden Class II, with no further description of partial vs. complete response. It appears that RCB Class II is a "moderate burden" of residual tumor after neoadjuvant therapy; could this be interpreted as a partial response in the Neoadjuvant Therapy--Treatment Effect code definitions?

The Solid Tumor Rules indicate p16 is a valid test to determine HPV status and can be used to code HPV-associated/-independent.

In this case, we do not know whether the HR-HPV test was done on cytologically malignant cells, or on benign cervical cells. It may be impossible to tell unless 100% of the cytology specimen is malignant, but we will not have access to that information. Also, HR-HPV testing is routine on Pap smears, so this testing does not mean the tumor cells specifically harbor HPV.

Patient had a total abdominal hysterectomy-bilateral salpingo-oophorectomy performed in January 2023 with final diagnosis of myxoid and epithelioid leiomyosarcoma.

Diagnosis comment states: The tumor is 15 cm per report. It grows in nests and poorly formed interanastomosing trabeculae and cords that are separated by abundant myxoid background. The cells have an epithelioid morphology with eosinophilic cytoplasm, large nuclei, and very prominent nucleoli. The mitotic activity is overall low ranging from 1 to 3/10 HPFs.

Immunohistochemical stains performed at the outside hospital showed diffuse positivity for SMA, desmin, caldesmon, and PR. They are negative for CD10, claudin-4, calretinin, HBM45, MART1 (rare weakly positive cells), PANCK, and SOX10. This immunohistochemical profile supports a smooth muscle derivation of this neoplasm. As this tumor is extensively myxoid, diagnostic criteria differ from the spindle cell leiomyosarcoma.

Per Solid Tumor Rules Other Sites, Table 16: Uterine Corpus Histologies, Epithelioid Leiomyosarcoma (8891/3) and Myxoid Leiomyosarcoma (8896/3) are both subtypes of Sarcoma, NOS (8800/3).  Per Rule H21, use a combination code when there are multiple specific histologies AND the combination is listed in Table 2 OR there are coding instructions for the combination in the applicable histology Tables 3-21 OR you receive a combination code from Ask A SEER Registrar.  Since there is no combination listed in Table 2 and there is no instruction for the combination in Table 16, how should the histology be coded for this tumor?

Example: Patient is diagnosed with grade 1 well-differentiated neuroendocrine tumor of the ileum, confirmed on ileocolic resection in 2023. The final diagnosis is a 2.8 cm ileal mass, with focal lymph-vascular invasion and a single 0.6 cm tumor deposit within mesenteric fat; primary tumor completely resected with widely negative margins and 10 regional nodes negative for malignancy.

According to AJCC, mesenteric masses less than 2 cm should be stated in the pathology report as being present and collected by registrars but do not affect stage. EOD Regional Nodes has a code for large mesenteric masses greater than 2 cm only. How should we record these smaller tumor deposits if they are not supposed to affect stage?

The patient had residual tumor following the 2018 transsphenoidal resection and underwent an additional surgery after the residual tumor increased in size. Since pituitary adenoma/pituitary neuroendocrine tumor (PitNET) is a new malignant neoplasm for cases diagnosed 2023 and later, should this be a new primary per M5? Or do we disregard the change in behavior and apply rule M2 (single tumor is a single primary) for this scenario?

Serous borderline tumor–micropapillary variant (8460/2, C569) was included in the ICD-O-3 Behavior Code/term updates effective 1/1/2018 but marked as Not Reportable for 2018.

There have been multiple additional updates to the ICD-O but no further clarification as to the reportability of this histology. ICD-O-3.2 currently lists serous borderline tumor, micropapillary variant (C569) as 8460/2 with no mention of reportability and no information provided in Includes/Excludes.

SINQ 20220032 instructs capturing this histology as reportable when diagnosed 1/1/2021 or later and occurring in the testis. The answer indicates this is reportable due to the /2 behavior code in ICD-O-3.2, but it does not specify that it is limited to specific sites.

Is serous borderline tumor, micropapillary variant reportable for ovary? If so, what dates apply? Is serous borderline tumor, micropapillary variant of the testis diagnosed after 1/1/2021 reportable?

The WHO Blue Books do not include dedifferentiated carcinoma as a valid histology for the breast.  However, there is known to be progression of ductal carcinoma that is essentially dedifferentiation of an estrogen receptor, progesterone receptor, and HER2 breast carcinoma to a triple negative "dedifferentiated" carcinoma which it appears this patient has. Whether we should accession this as a separate 8020/3 primary per M14 is unclear and the Solid Tumor Manual does not address this scenario.