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SEER Inquiry System - Report
Produced: 12/21/2025 10:39 AM
Question 20110044
Inquiry Details
References:
#1: 2010 SEER Manual. Appendix C
#2: Subject matter expert
Question:
MP/H Rules/Histology--Corpus uteri: What are the histologies for the primaries to be reported when the endometrium contains two separate tumors composed of adenocarcinoma with multiple differentiations as well as a separate small focus of clear cell carcinoma? See Discussion.
Discussion:
The resected specimen showed, "Adenocarcinoma of endometrium with the following features: Histologic type: Endometrioid with squamous and focal clear cell differentiation. A second focus of endometrial adenocarcinoma is present in the fundus with admixed complex atypical hyperplasia in a polypoid, non-invasive mass. The second tumor is endometrioid with secretory differentiation. COMMENT: The tissue in between the two tumors is sampled, and contains foci of endometrial adenocarcinoma that is superficially present within the endometrium, as well as a small focus of clear cell carcinoma measuring 0.2 cm."
Per MP/H rules M17, this is counted as multiple primaries because the histology codes differ at the third digit: 8323/3, 8382/3, 8310/3. The Multiple Primary rules make no reference to the histology tables. There is also no rule to ignore the in situ tumor. In addition, the histology table in the 2007 MP/H Rules Manual for Other Sites does not include "secretory differentiation" as a type of GYN malignancy.
Answer:
After consultation with our expert pathologist, the decision is report this case as a single primary. There was some confusion about how to apply the current MP/H rules to this pathology report given 1) the definition of M16 and M17 and 2) the likelihood for a single endometrial primary to present with several differentiations. According to our expert pathologist, "I would regard this case as a single endometrial primary with extensive endometrial involvement and several types of differentiation, all of which are seen in endometrial carcinomas."
Next, the Multiple Primary and Histology Coding Rules Manual is the correct source for coding histology for cases diagnosed 2007 or later.
The following steps are used to determine the histology code.
Open the Multiple Primary and Histology Coding Rules manual. For an endometrial primary, use the Other Sites Histo rules to determine the histology code because endometrium does not have site specific rules.
Start with the MULTIPLE TUMORS ABSTRACTED AS A SINGLE PRIMARY module, Rule H18. The rules are intended to be reviewed in consecutive order within the module from Rule H18 to Rule H31. You stop at the first rule that applies to the case you are processing.
Code the appropriate combination/mixed code (Table 2) when there are multiple specific histologies. GYN malignancies with multiple types of adenocarcinoma have histology coded to 8323/3 [mixed cell adenocarcinoma] per rule H30.
