Quantification of ER/PR expression in ovarian low-grade serous carcinoma

Case reports suggest that hormonal therapy may be a useful treatment option for low-grade serous carcinomas (LGSC) but the clinical value remains uncertain. We hypothesized that LGSCs show a constitutive high hormone receptor expression and that type diagnosis may be sufficient to initiate hormonal therapy.

We assessed ER and PR expression on 27 LGSC, 69 high-grade serous carcinomas (HGSC), 36 serous borderline tumors (SBOT), and five normal fallopian tubes using three different platforms/antibodies on tissue microarrays. Staining from the Leica Bond Max and DAKO PharmDx platforms was evaluated using the Allred score. Quantitative fluorescence immunohistochemistry was performed using the HistoRx AQUAnalysis platform. A second cohort of 12 LGSC and 183 HGSC was assessed using the HistoRx AQUAnalysis platform. Welch ANOVA or Fisher's Exact Test was used to compare differences in the histological types for each platform. Nonparametric bivariate density plots were used to graphically demonstrate the relationship between ER and PR for the various histological types.

LGSC have higher ER and PR expression compared to HGSC but significantly less than FT and SBOT. Nonparametric bivariate density revealed two populations of LGSC: one fifth of LGSC are ER high/PR high expressers similar to SBOT but the majority show low ER/PR expression more like HGSC.

Quantitative assessment of ER/PR expression using the HistoRx AQUAnalysis platform may be useful as a predictive diagnostic for hormonal therapy in LGSC, assuming that only the fraction of double high expressers benefit from hormonal treatment.