Cytoplasmic CD24 expression in advanced ovarian serous borderline tumors.

Objectives: CD24, originally described as a B-cell marker, has been revealed as one of the candidate molecular markers of epithelial ovarian cancer. We aimed to determine the pattern and extent of CD24 expression in ovarian serous tumors and to clarify its relationship with pathological parameters, especially those associated with the early events of tumor progression in serous tumors of borderline malignancy.
Methods: A total of 114 ovarian serous tumors, including 9 adenomas, 34 borderline, and 71 carcinomas, were analyzed immunohistochemically using a CD24 monoclonal antibody on paraffin blocks.
Results: In normal epithelium and serous cystadenomas, the CD24 expression was localized to the apical membranous portion. In some of borderline tumors (26.4%), additional cytoplasmic expression was observed. The cytoplasmic expression of CD24 in borderline tumors was associated with microinvasion (P = 0.001) and omental implants (P = 0.033) with statistical significance. Serous adenocarcinomas showed strong diffuse cytoplasmic expression of CD24, which was significantly associated with shortened survival rate both in univariate (P = 0.011) and multivariate (P = 0.009) analysis.
Conclusion: The loss of apical localization with the acquisition of the cytoplasmic staining of CD24 protein is a surrogate marker of stromal invasion in ovarian serous tumors of borderline malignancy. Furthermore, the increase in the cytoplasmic expression of CD24 protein is a strong independent molecular marker for shortened survival rate of patients with ovarian serous adenocarcinomas.