Commentary (Trimble/Trimble): Update on Low Malignant Potential Ovarian Tumors

Nomenclature Various names have been applied to this entity. These include “ovarian tumors of low malignant potential,” “borderline ovarian tumors,” “atypical proliferating ovarian tumors,” and even “borderline ovarian carcinomas.” Each of these terms has its drawbacks. “Low malignant potential” suggests that these tumors have a certain propensity to become malignant. In fact, as Kurman and Trimble illustrated, the rate of malignant transformation for LMP ovarian tumors is lower than that for uterine leiomyomata, which undergo malignant transformation to leiomyosarcoma (0.1%).[1] The name “borderline ovarian tumors” suggests that these tumors represent an intermediate biological stage between benign ovarian cysts and invasive carcinoma. In fact, various molecular biology studies have demonstrated that LMP tumors are not precursors to cancer.[2] “Atypical proliferating tumors” is a histologic characterization that has not yet gained widespread acceptance among either pathologists or gynecologists. “Borderline carcinoma” suggests that tumors are invasive carcinomas warranting aggressive surgical treatment, followed by adjuvant chemotherapy. However, the natural history of LMP ovarian tumors suggests that conservative surgery without cytotoxic chemotherapy will suffice for most women. Histology Should the histologic subtypes of LMP ovarian tumors be made more specific? As Menzin explains, the subtypes that have been reported include serous, mucinous, endometrioid, clear cell, and Brenner. Many series and case reports fail to distinguish between these subtypes, however, or to state the histologic criteria used to subtype or provide photomicrographs that would allow the reader to confirm the subtype.[2] Endometrioid, clear cell, and Brenner ovarian tumors of LMP are exceedingly rare. Serous LMP ovarian tumors are the most common subtype. Furthermore, some authors fail to distinguish between primary peritoneal carcinoma with LMP-type implants in the ovaries and ovarian tumors of LMP with LMP-type implants elsewhere in the abdomen.[2] In the past, pseudomyxoma peritonei (“jelly belly”) was classified as a mucinous LMP tumor. More recently, Ronnett and others have shown that the vast majority of these cases arise from gastrointestinal primary tumors, usually in the appendix.[3] Most true mucinous tumors of LMP are confined to one or both ovaries. Epidemiology Ovarian tumors of LMP tend to occur in women at younger ages than does invasive ovarian cancer. Most series of ovarian tumors reported in adolescents, young adults, or pregnant women contain a large proportion of ovarian tumors of LMP. As Menzin points out, pregnancy, lactation, and oral contraceptives reduce the risk of ovarian tumors of LMP just as they reduce the risk of invasive ovarian cancer. Women with BRCA1 and BRCA2 mutations, who are at increased risk for ovarian cancer, do not appear to be at greater risk for ovarian tumors of LMP. The use of fertility drugs appears to increase the incidence of LMP tumors but not ovarian cancer. Screening