[1109] Immunohistochemical Panel of p16, p63 and Ki-67 Is Useful in Distinguishing Mucinous Adenocarcinomas of Endometrium (MUC-ADs) from Microglandular Hyperplasia (MGH) of Endocervix.

Anupma Nayak, Nora J Morgenstern, Tawfiqul A Bhuiya. Albert Einstein College of Medicine at Long Island Jewish Medical Center, New Hyde Park, NY

Background: MUC-ADs of endometrium represent 10% of all endometrial carcinomas. Owing to their overall bland cytology and frequent microglandular architecture, these lesions are difficult to differentiate from benign MGH of endocervix, particularly in the small volume endometrial curettings/biopsies. This study aims to determine a useful immunohistochemistry (IHC) panel for distinguishing MUC-AD of endometrium from MGH of endocervix.
Design: A total of 23 cases of MUC-AD of endometrium were selected from our institution's pathology database between the years 2006 to 2010. Eleven cases of MGH of endocervix were used as control group. All cases were stained for p63, p16, vimentin, CEA, CD10, and Ki-67 antigens. Staining intensity and the percentage positivity for each stain was evaluated.
Results: None (0%) of the MGH endocervix cases were positive for p16 whereas, 21/23(91.3%) MUC-ADs of endometrium cases showed moderate to strong nuclear and cytoplasmic staining for p16 in ≥50% of tumor (avg. staining, 76.4%). Nuclear staining for p63 was noted in all(100%) the MGH cases (avg. staining, 93.2%) in a distinct continuous, linear and basal pattern. Although, 20/23(87%) MUC-ADs of endometrium showed nuclear positivity for p63, the pattern was focal, random and scattered (avg. staining 16.1%). CEA highlighted the surface and apical cytoplasm of the mucinous epithelium in all (100%) the MUC-ADs of endometrium (avg. staining, 62.8%). However, 4 of 11 MGH cases (36.4%) also expressed positivity for CEA (avg. staining, 17%). Ki-67 staining index was >5% in only 1/11(9%) cases of MGH of endocervix, in contrast to 17/23(73.9%) cases of MUC-ADs of endometrium. All 23(100%) cases of MUC-ADs showed basal cytoplasmic/membranous epithelial staining for vimentin (avg. staining, 70.2%). However, 4 of 11(36.4%) MGH cases also showed positivity in ≥50% of epithelial cells. CD10 was positive in stromal cells of 23/23(100%) cases of MUC-ADs of endometrium and 7/11(63.6%) cases of MGH.
Conclusions: A combined IHC panel of p16, p63 and Ki-67 is useful in distinguishing MUC-ADs of endometrium from MGH of endocervix. Diffuse and strong expression of p16, lack of continuous, linear and basal staining for p63, and increased Ki-67 index (>5%) strongly favors a diagnosis of MUC-ADs of endometrium over MGH of endocervix. CD10, CEA and Vimentin are non-contributory in this context. The exact mechanism of diffuse p16 expression in MUC-ADs of endometrium is unclear.
Category: Gynecologic & Obstetrics

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 154, Wednesday Afternoon

 

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