Evaluation of Microinvasion and Lymph Node Involvement in Ovarian Serous Borderline/Atypical Proliferative Serous Tumors

Most of the literature on serous borderline/atypical proliferative serous tumors (SBT/APSTs) shows no effect of microinvasion or lymph node involvement on outcome. This study is a morphologic and immunohistochemical analysis of the cells comprising SBT/APSTs, microinvasion, lymph node involvement, and low-grade serous carcinoma (LGSC) in an attempt to explain this unusual behavior. We found that the cells in microinvasion and in lymph nodes were morphologically similar to the cells in SBT/APSTs but differed significantly from the cells in LGSCs. In addition, one particular population of cells, those with abundant eosinophilic cytoplasm (eosinophilic cells), in SBT/APSTs, microinvasion, and lymph nodes showed a significant loss of expression of ER, PR, and WT-1 compared with the cuboidal/columnar tumor cells, both in cases of microinvasion (P