Low-Grade Serous Tumors of Ovary

The creation of the category of borderline/atypical proliferative tumors in the World Health Organization Classification of Ovarian Tumors in 1973 prompted extensive investigation of the clinicopathologic and genetic features of low-grade serous ovarian tumors (borderline tumors/atypical proliferative tumors, noninvasive micropapillary tumors, and invasive low-grade serous carcinomas). The clinicopathologic studies of these tumors resulted in clarification of the prognostic significance of several histologic features of the ovarian tumors and their associated peritoneal lesions. The genetic studies resulted in a reassessment of the relationship between low-grade and high-grade serous carcinoma and their differing pathways of origin. This review focuses on several of the morphologic findings, their diagnostic criteria, differential diagnosis and biologic significance, and discusses the dualistic classification of serous carcinomas into high-grade and low-grade tumors.