Serous tumors of the ovary (borderline tumors and carcinomas) with and without micropapillary features.

The articles by Gilks et al. (1) and Singer et al. (2) in this issue of the Journal explore practical and conceptual aspects of great interest relating to serous tumors of the ovary: pathologic findings of prognostic importance in advanced stage serous borderline tumors (SBTs) and genetic alterations suggesting that SBTs and serous carcinomas develop through separate pathways, i.e., a dualistic model of serous carcinogenesis. Since the early 1970s, serous tumors of the ovary have been classified according to their degree of epithelial proliferation into benign, borderline (low malignant potential), and carcinomas (3,4). This subdivision proved to be important because it correlates with the clinical behavior in the vast majority of cases. It became progressively apparent, however, that the natural history of the serous borderline tumors (SBTs) differs considerably from that of the other two subcategories of serous neoplasms. In other words, whereas the behavior of the benign serous tumors and carcinomas can be easily predicted by conventional histopathologic examination, the serous tumors of low malignant potential exhibit borderline histologic and biologic features. Initially defined as intermediate or semimalignant tumors, SBTs are characterized by epithelial proliferation, lack of destructive ovarian stromal invasion, and an overall prognosis far better than that of serous carcinomas even when the tumor has implanted on the peritoneum. Almost 90% of the patients with SBTs (and practically all stage I tumors) are cured by surgical removal of the tumor alone. However, the identification of the rare ovarian SBTs associated with an unfavorable prognosis did not meet with success when only features of the ovarian tumor were considered. In the late 1980s attention was focused on the histologic characteristics of the peritoneal implants that occur in approximately 30% of the cases (5,6). Classification of the implants into noninvasive and invasive (with the former being subdivided into epithelial and desmoplastic types) proved to be of paramount prognostic significance (6). Presently, there is convincing evidence in the literature that the only fatal cases of SBT are those associated with invasive implants (5–10), and these rare tumors are best, although not always effectively, treated with chemotherapy. Over the last decade, pathologists have learned to recognize the microscopic features of invasive implants, whether they represent true implants or independent primary tumors. The distinction between invasive and noninvasive implants has largely relied on the finding of destructive invasion of the normal underlying tissue. In adopting this practice, pathologists have insisted on the importance of searching for the peritoneal lesions, and have advised not to administer adjuvant therapy to patients with noninvasive implants lacking carcinoma cells. Recently, Kurman and his collaborators (8,11) proposed that a small subset of SBTs with a micropapillary architecture and an allegedly higher frequency of invasive peritoneal implants should be designated “micropapillary serous carcinomas. ” Based on the overall favorable prognosis of the nonmicropapillary SBTs, these investigators have recommended abandoning the borderline category of serous tumors, referring to them as either benign (benign and typical SBTs) or malignant types (the latter including serous tumors with a micropapillary architecture and lacking destructive stromal invasion). The question of whether SBTs with a micropapillary pattern (SBT-MP) are more likely to be associated with invasive implants and an adverse prognosis has greatly renewed interest in this category of serous tumors and resulted in several recent publications (9,10,12,13). At least four of these investigations have failed to demonstrate that the overall survival of patients with advanced stage SBTsMP differs from that of patients with typical SBTs (9, 10,12,13). They have shown that bilaterality, ovarian surface growth, and advanced stage are more common features of SBTs-MP than of typical SBTs, but a strong From the Department of Pathology, Hospital de la Santa Creu i Sant Pau Autonomous University of Barcelona, Barcelona, Spain International Journal of Gynecological Pathology 22:25–28, Lippincott Williams & Wilkins, Baltimore © 2002 International Society of Gynecological Pathologists