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SEER Inquiry System - Report
Produced: 06/14/2026 10:16 PM
Question 20170066
Inquiry Details
References:
2016 SEER Manual, 78. Primary Site
Question:
2016 SEER Manual/Primary Site--Corpus Uteri: Is the primary site C541 (endometrium) or C543 (uterine fundus) when the histology states endometrial adenocarcinoma, endometrioid type, but tumor site states fundus? See Discussion.
Discussion:
Pathology--Final description: Uterus, cervix, bilateral fallopian tubes and ovaries, total hysterectomy and bilateral salpingo-oophorectomy: Endometrial adenocarcinoma, endometrioid type, well differentiated, FIGO 1/3. Myometrial invasion: focal myometrial invasion (30% of myometrium) Tumor size: 2 x2 cm Tumor site: Fundus, exophytic/polypoid lesion Gross description: The 3.0 cm in length by 2.5 cm in diameter triangular endometrium is tan-red and smooth with a 2.0 x 2.0 cm tan-pink, exophytic fundic mass which extends on to both anterior and posterior aspects, 4.1 cm from the os.
Answer:
We recommend coding endometrium, C541, as the primary site for this case. While coding to fundus would not be incorrect, according to our expert pathologist consultant, "it is more appropriate in a setting in which the region of the uterus is of importance, e.g. with a myoma or a myosarcoma, or if the endometrioid carcinoma were NOT in the endometrium but arising in a focus of adenomyosis within the fundic myometrium."
