Miscellaneous types of surface epithelial neoplasms. The well-differentiated end of the morphologic spectrum of endometrioid, clear-cell, and Brenner tumors and mixed epithelioid tumors of low malignant potential of müllerian type.

Benign ovarian neoplasms with endometrioid or clear-cell differentiation are rare, but benign Brenner tumors are not unusual. A subgroup of endometrioid, clear-cell, and Brenner neoplasms, characterized by morphologic features intermediate between benign and malignant, has been labelled by various investigators as borderline, of low malignant potential (LMP), or proliferating. This chapter reviews the definition of each of these cell types, evaluates the significance of the LMP category, and concludes with a discussion of well-differentiated ovarian neoplasms with mixed differentiation of the müllerian type.