[1195] PAX8 Expression Is Useful To Distinguish Dedifferentiated Endometrioid Adenocarcinoma from Grade III Endometrioid Adenocarcinoma

Zaibo Li, Faye Gao, Wei Hong, Chengquan Zhao. UPMC Magee-Womens Hospital, Pittsburgh, PA; Conemaugh Memorial Medical Center, Johnstown, PA

Background: Dedifferentiated endometrioid adenocarcinoma (DEAC) of the uterus or ovary is characterized by the coexistence of low grade endometrioid adenocarcinoma (FIGO grade I/II) and an undifferentiated carcinoma (UC) with solid sheet of medium-sized monotonous epithelial cells. This admixed carcinoma has not been widely recognized because the solid areas of UC have usually been misdiagnosed as solid form of FIGO grade III endometrioid adenocarcinoma. These tumors have been shown to be clinically aggressive; therefore, accurate diagnosis is necessary for proper patient management.
Design: DEAC cases were retrieved from our pathology database. All H&E slides were reviewed by two pathologists to confirm the diagnosis and exclude other entities. Immunohistochemical stains were assessed and clinical information was obtained.
Results: 11 DEACs including 7 endometrial and 4 ovarian origins were identified. All patients presented at advanced stages with 72% of cases showing vascular invasion, 64% showing lymph node metastases and 27% showing distal metastases. The UC components were composed of diffuse sheets/solid nests of medium-sized epithelial cells with scant to moderate cytoplasm, uniform vesicular nuclei and inconspicuous nucleoli. All cases showed diffuse and strong nuclear PAX8 staining in FIGO I/II endometrioid component and no PAX8 staining in UC components (Figure 1A/1B). In control group of 11 FIGO grade III endometrioid adenocarcinomas, PAX8 was positive in both solid and glandular areas (Figure 1C/1D). UC components of DEACs are variably positive for cytokeratin AE1/3 (88%), CAM5.2 (86%) and hormone receptors (ER or PR, 66%). All patients received chemoradiation therapy after surgery. Follow-up data were available for 8 patients and revealed all patients had either recurrent or metastatic diseases within 3 years except for one patient with free of tumor for 3 years.

Conclusions: The recognition of DEAC with low-grade endometrioid adenocarcinoma is extremely important due to its aggressive behavior. Our study results indicated that the unique PAX8 staining pattern in DEAC can be very helpful to distinguish DEAC from FIGO grade III endometrioid adenocarcinoma.
Category: Gynecologic & Obstetrics

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 123, Tuesday Morning


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