Gain of OGP, an estrogen-regulated oviduct-specific glycoprotein, is associated with the development of endometrial hyperplasia and endometrial cancer.

PURPOSE Lesions in the endometrium are difficult to differentially diagnose. The present study examined whether oviduct-specific glycoprotein is differentially expressed in normal, hyperplastic, and malignant endometrium. EXPERIMENTAL DESIGN The expression of oviduct-specific glycoprotein was characterized by immunohistochemical methods with whole sections of endometrium from 90 women. An endometrial cancer tissue microarray with 200 cases of endometrial cancer was also assessed for oviduct-specific glycoprotein, estrogen receptor, and PTEN expression. RESULTS In normal endometrium, there was focal oviduct-specific glycoprotein expression in the basalis layer, where the stem cells reside, in 10 of 15 cases. On average, atypical hyperplastic endometria stained more intensely than hyperplastic endometria (P = 0.017), whereas the percentage of positively stained cells was not significantly different. The mean staining indices (intensity x percentage of positive cells score) for hyperplasia and atypical hyperplastic were 4.7 and 5.5 and were significantly higher than staining indices seen in normal cycling endometria or well-differentiated endometrioid endometrial carcinomas (P < 0.0001 and P < 0.001, respectively). The endometrial cancer tissue microarray showed that of 139 endometrioid endometrial carcinomas, 11 cases were strongly oviduct-specific glycoprotein positive, whereas the other 128 cases were negative or weakly positive. Analysis of Kaplan-Meier curves with log-rank statistics showed a trend toward significance, with strong oviduct-specific glycoprotein staining serving as a predictor of good prognosis (P = 0.1). There was a significant positive correlation between oviduct-specific glycoprotein staining and loss of PTEN in the cases of endometrial cancer (P = 0.004). CONCLUSIONS Oviduct-specific glycoprotein may be a useful diagnostic adjunct to more accurately classify premalignant and early malignant change in the endometrium, improving on the current irreproducible histologic classification system.