Expression of H1.5 and PLZF in granulosa cell tumors and normal ovarian tissues: a short report.

PURPOSE: Ovarian granulosa cell tumors (GCTs) typically exhibit an excellent prognosis, but their recurrences are associated with high mortality rates. In the past, immunohistochemistry (IHC)-based approaches have been used to facilitate the distinction between GCTs and other, more frequently occurring, primary or metastatic tumors. The purpose of this study was to assess the added value of H1.5 and PLZF protein expression in the correct delineation of GCTs. METHODS: Consecutive 5-μm thick sections from routinely fixed and paraffin embedded tissues from 30 GCTs and 33 benign ovaries were processed for IHC using anti-PLZF and anti-H1.5 monoclonal antibodies. The respective protein staining intensities and distributions were quantified into reported scores for all tissue samples. Student's t-test and Fisher's exact test were used to compare the mean scores for each group. A p-value of <0.05 was considered statistically significant. Also, both the sensitivity and the specificity of the two antibodies were evaluated. RESULTS: A statistically significant difference in the expression of H1.5 between the GCT and normal ovary groups was observed (p < 0.0001). Normal ovarian tissues were found to strongly express H1.5, whereas GCTs were found to weakly express this protein. In contrast, PLZ expression was not found to be significantly different between both study groups. CONCLUSIONS: From our results we conclude that H1.5 is down-regulated in GCTs compared to normal ovarian tissues. Additional investigations on larger and more heterogeneous study populations, and on the molecular mechanism (s) underlying down-regulation of the H1.5 protein, may further substantiate the use of H1.5 as a diagnostic/prognostic marker and, in addition, provide insight into the pathogenesis of GCTs.