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The only Other Sites H Rule related to extramammary Paget disease is included in the Multiple Tumors Abstracted as a Single Primary module. Rule H28 instructs one to code the histology of the underlying tumor when there is extramammary Paget disease and an underlying tumor of the anus, perianal region, or vulva. Therefore, a vulvar extramammary Paget disease with underlying adenocarcinoma is coded as adenocarcinoma (8140/3), and not extramammary Paget disease (8542/3).

However, there is no M Rule confirming extramammary Paget disease and the underlying adenocarcinoma are a single primary (i.e., multiple tumors abstracted as a single primary) making it difficult for one to use the Multiple Tumors Abstracted as a Single Primary H rules module.

We recognize this is a longstanding histology coding rule, but how are registrars supposed to arrive at Rule H28 when the M Rules must be applied first and do not instruct one to accession a single primary? Moreover, if this is to be a single primary (per rule M2), why is there no H Rule in the Single Tumor module?

Example 4:  Esophageal biopsy with diagnosis of “focal areas suspicious for adenocarcinoma in situ.” Diagnosis on partial esophagectomy specimen “with foci of high grade dysplasia; no invasive carcinoma identified.” Do not accession the case. The esophagectomy proved that the suspicious biopsy result was false.

Appendix E2 #32 of the SEER Manual states high grade dysplasia in site other than stomach, small intestines, and esophageal primary sites are not reportable. Does this mean high grade dysplasia is reportable for esophagus primaries?

The term “poorly differentiated carcinoma (NOS)” is listed as related to “undifferentiated carcinoma (NOS)” in the ICD-O 3.2. It is also listed in the Solid Tumor Rules for Urinary Table 2 (Urinary subtypes), Other Sites Table 16 (uterine corpus primaries) and Table 19 (vulvar primaries).

Are these the only sites in which one should code “poorly differentiated carcinoma (NOS)” as 8020 (undifferentiated carcinoma)?

How is histology coded if the only microscopic confirmation is from a metastatic site showing “poorly differentiated carcinoma” (NOS) or “invasive carcinoma, poorly differentiated” (NOS)?

Example 1: Primary pancreatic cancer diagnosed on imaging and confirmed with liver mets core biopsy showing “poorly differentiated carcinoma.” Immunostaining pattern was non-specific. No further workup or treatment was planned.

Other Sites - Table 11 (Pancreas Histologies) includes undifferentiated carcinoma (8020/3) as a valid histology; however, the synonyms/subtypes/variants do not mention poorly differentiated carcinoma. How should histology be coded for this case?

Example 2: Hemicolectomy with cecal tumor final diagnosis of “invasive carcinoma, poorly differentiated” and synoptic summary listing “Histologic type: Invasive carcinoma. Histologic grade: G3 of 4: poorly differentiated.”

Colorectal Table 1 (Specific Histologies and Subtypes/Variants) includes undifferentiated adenocarcinoma/carcinoma 8020 as a subtype of adenocarcinoma NOS. There is no mention of poorly differentiated in this context. How should histology be coded for this case?

SEER Program Coding and Staging Manual: Reportability – Reportable Diagnosis List indicates pancreatic intraepithelial neoplasia (PanIN II) (C250-C259) is reportable.

However, the ICD-O-3.2 lists “Glandular intraepithelial neoplasia, grade II” and “Glandular intraepithelial neoplasia, low grade” as histology code 8148 with behavior of /0 (benign).

In previous STR versions and the ICD-O-3.2, SFT/hemangiopericytoma, WHO G1 is 8815/0 and only SFT/hemangiopericytoma, WHO G2 was 8815/1. However, Table 6 (Non-Malignant CNS, Specific Histologies, NOS, and Subtypes/Variants) was changed in the 2025 updates to indicate both G1 and G2 SFT/hemangiopericytoma are 8815/1.

No date range was provided for this change in the STR and the behavior of this tumor was not updated by the standard setters in other references (i.e., ICD-O-3.2). The behavior of G1 SFT/hemangiopericytoma was not updated in the 2025 ICD-O-3.2 updates. If the ICD-O-3.2 was the source of this change, should this have been documented in the 2025 NAACCR Implementation Guidelines? However, the 2025 NAACCR Implementation Guidelines indicates, "There are no ICD-O-3 changes for 2025." Is this behavior change in 2025 Solid Tumor Rules updates an error? Should the behavior of SFT/hemangiopericytoma, WHO G1 remain /0? 

We have questions regarding reportability of some terms/diagnoses after a review of EIN cases back to 2021. While some seem synonymous with EIN, others have different terms in the pathology report though the physician is treating as if they have the diagnosis.  

1. Atypical glandular epithelium

Scenario: Endometrium biopsy with ablation performed at Facility A on 8/7/2024 showed atypical glandular epithelium. Patient was sent to Facility B where the total abdominal hysterectomy/bilateral salpingo-oophorectomy (TAH/BSO) on 9/20/2024 showed other reactive fibrosis and obliterated architecture compatible with history of ablation. Is atypical glandular epithelium synonymous with and coded as EIN?

2. Isthmic-type mucosa with focal severe atypia

Scenario: Endometrium biopsy showed isthmic-type mucosa with focal severe atypia.  Then Facility B did TAH/BSO that showed no evidence of high grade dysplasia, atypical hyperplasia, or carcinoma.

3. Simple hyperplasia without atypia 

Scenario: Endometrial biopsy pathology states simple hyperplasia without atypia and the TAH/BSO is either negative or has the same histology; however, the treating physician is stating EIN. 

4. EIN/CAH or focal EIN/CAH

Scenario: Biopsy showed EIN/CAH but the total abdominal hysterectomy/bilateral salpingo-oophorectomy (TAH/BSO) pathology or the Mirena IUD treatment operative note states no EIN/CAH/Atypical hyperplasia. Are these reportable, similar to an in situ when the re-excision lumpectomy or mastectomy is negative or no residual disease?