[1093] Combined p53 and p16 Expression Is Useful To Distinguish between Endometrial Serous and Endometrioid Carcinomas
N Ursani, R Saleh, A Lytwyn, D Daya, C Ceballos, L Elit, M Sur, K Onuma. McMaster University, Hamilton, ON, Canada; Universitiy of British Columbia, Vancouver, BC, Canada
Background: p53 Immunohistochemistry is a widely used diagnostic test to distinguish between endometrial serous carcinoma (SC) and a subset of endometrioid carcinoma (EC), however, its diagnostic limitatiion remains a practical problem. Immunohistochemical overexpression of p16 has been also reported in SC. Although it has recently been suggested that an immunohistochemical panel including these two markers be used to overcome the limitations of using p53 alone, the diagnostic value of such a panel has not been well studied. In this study, we assessed the immunohistochemical profile of SC and EC using a panel of five immunohistochemical markers including p53 and p16 to test the diagnostic value of a panel.
Design: Fifty two hysterectomies reported with SC and 50 with EC were retrieved from the surgical pathology file. Three gynecologic pathologists independently reviewed the HE slides. Equivocal cases or those with mixed histology were excluded; thus 32 SC and 46 EC FIGO 1 or 2 formed the study set. Immunohistochemical stains for estrogen receptor (ER), progesterone receptor (PR), p53, p16 and beta-catenin (Bcat) were performed on a representative section from each case. Two pathologists, masked to the review diagnosis, independently evaluated the immunohistochemistry (IHC) using qualitative and quantitative criteria. Any discrepancies among pathologists were resolved on consensus review.
Results:
Comparison of immunohistochemical expression | SC (n=32) | EC (n=46) | | ER | 15 (47%) | 38 (83%) | | PR | 13 (41%) | 43 (94%) | | p53 | 27 (84%) | 3 (7%) | | p16 | 26 (81%) | 3 (7%) | | Bcat | 0 (0%) | 13 (28%) | | p53+ p16+ Bcat - | 23 (72%) | 1 (2%) | | p53+ p16- Bcat - | 4 (13%) | 2 (4%) | | p53- p16+ Bcat - | 3 (9%) | 2 (4%) | | p53- p16- Bcat + | 0 (0%) | 13 (28%) | | p53- p16- Bcat- | 2 (6%) | 28 (61%) |
Accuracy of immunohistochemistry for SC and EC| Reference standard | IHC | Sensitivity | Specificity | +Likelihood Ratio | | SC | p53+ | 84% | 93% | 12 | | SC | p53+p16+ | 75% | 98% | 38 | | EC | p53- | 93% | 84% | 6 | | EC | p53-p16- | 89% | 94% | 15 |
Conclusions: Double positive or double negative p53 and p16 profiles substantially increase the positive likelihood ratios for SC and EC, respectively, compared to p53 alone. As an individual marker, Bcat was exclusively seen in EC, but in only a minority of cases. Hormone receptors showed substantial overlap between SC and EC, and did not contribute to the tumor distinction.
Category: Gynecologic
Monday, March 9, 2009 9:30 AM
Poster Session I Stowell-Orbison/Autopsy Award # 166, Monday Morning
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