MICROPAPILLARY SEROUS CARCINOMA OF THE OVARY - A DISTINCTIVE LOW-GRADE CARCINOMA RELATED TO SEROUS BORDERLINE TUMORS

According to the International Federation of Gynecology and Obstetrics (FIGO) and the World Health Organization (WHO), stromal invasion, def ined as destructive infiltrative growth, is the sole criterion used to distinguish serous borderline tumors from invasive serous carcinomas of the ovary. Although this criterion effectively identifies most mali gnant tumors, it does not permit the identification of a small subset of well-differentiated ovarian carcinomas that do not display destruct ive infiltrative growth but that may be associated with malignant beha vior. In this study, we describe a group of such serous neoplasms that have distinctive morphologic features and that are often associated w ith progressive, invasive disease. We have designated these tumors mic ropapillary, serous carcinomas (MPSC). They are characterized by a fil igree pattern of highly complex micropapillae arising directly from la rge, bulbous papillary structures. The micropapillae are covered by ro und to cuboidal cells with a high nuclear-to-cytoplasmic ratio. Typica l serous borderline tumors tend to display a hierarchical pattern of b ranching terminating in small papillae or tufts, and the cells coverin g the papillae tend to be more columnar and often ciliated compared wi th cells of MPSC. We reviewed more than 400 cases of serous ovarian bo rderline tumors and well-differentiated serous carcinomas and identifi ed 26 cases of MPSC. Seventeen tumors lacked destructive infiltrative growth (noninvasive), and nine contained areas of invasion ranging fro m minimal to extensive. Fight of the 26 tumors were stage I, and none of the patients developed recurrence whether or not their tumors had d emonstrable invasion. In contrast, of the 16 women presenting with sta ge II disease or higher and who had more than 1 year of follow-up, eig ht (50%) have either died of intra-abdominal carcinomatosis or are ali ve with carcinoma. Twenty-four (92%) of MPSCs contained areas of serou s borderline tumor. The frequent association of MPSCs with serous bord erline tumors suggests that MPSCs arise from the latter and may accoun t for the few cases of serous borderline tumors that have been associa ted with progression to invasive carcinoma.