A 23-year-old female presents with pelvic pain and is found to have an ovarian mass of the left ovary that measures 3 cm in diameter. Grossly, the mass consists of multiple cystic spaces. Histologically, these cysts are lined by tall columnar epithelium, with some of the cells being ciliated. What is your diagnosis of this ovarian tumor, which histologically recapitulates the histology of the fallopian tubes?

The surface epithelial tumors of the ovary are derived from the surface celomic epithelium, which embryonically gives rise to the Mullerian epithelium. Therefore these ovarian epithelial tumors may recapitulate the histology of organs derived from the Mullerian epithelium. For example, serous ovarian tumors are composed of ciliated columnar serous epithelial cells, which are similar to the lining cells of the fallopian tubes. Endometrioid ovarian tumors are composed of nonciliated columnar cells, which are similar to the lining cells of the endometrium. Mucinous ovarian tumors are composed of mucinous nonciliated columnar cells, which are similar to the epithelial cells of the endocervical glands. Other epithelial ovarian tumors are similar histologically to other organs of the urogenital tract, such as the clear cell ovarian carcinoma and the Brenner tumor. Clear cell carcinoma of the ovary is similar histologically to clear cell carcinoma of the kidney, or more accurately, the clear cell variant of endometrial adenocarcinoma or the glycogen-rich cells associated with pregnancy. The Brenner tumor is similar to the transitional lining of the renal pelvis or bladder. This ovarian tumor is associated with benign mucinous cystadenomas of the ovary Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition