Department of Pathology, Sinai Hospital of Baltimore Pathology, Baltimore, MD, USA
KeywordsBorderlineAtypical proliferativeSerousMucinousEndometrioidBrennerClear cellSex cord stromalTeratoma
The ovary is a fairly straightforward organ as far as the pathologist is concerned. Find tumor; identify tumor. No messing around with non-neoplastic pathology, margins, depth of invasion, reactive lesions, and so on. If it looks malignant, it probably is.
Normal Histology and Definitions
Surface epithelium : essentially a mesothelial lining. It is easily rubbed off the surface, so you do not always see it.
Stroma : the ovarian stroma is blue and spindly, with short, crisscrossing fascicles. Most of the cells in the stroma are fibroblasts (Figure 15.1).
Ovarian stroma with follicle. Typical ovarian stroma is blue and cellular, with a vaguely fascicular or storiform pattern. A small primary follicle is seen with the central oocyte (arrow) and a ring of granulosa cells (arrowhead).
Sex cord cells : the hormone-secreting supporting cells of the ovary, the thecal cells and granulosa cells. The thecal cells, under luteinizing hormone (LH) stimulation, secrete androgens, and the granulosa cells, under follicle stimulating hormone (FSH) control, convert androgens to estrogen. Together they nurture an oocyte to ovulation. These cells are analogous to Sertoli and Leydig cells in the testis.
Follicles : characterized by a halo of thecal cells outside a ring of granulosa cells (Figure 15.1), all surrounding the giant oocyte (germ cell). In developing follicles, the granulosa cells form Call–Exner bodies, rosettes of granulosa cells surrounding pink globules.
Luteinized : similar to “decidualized,” luteinized indicates cells that have become plump with abundant pink cytoplasm.
Corpus luteum : a newly ovulated follicle (Figure 15.2). The capsule of luteinized granulosa cells collapses in on itself, becoming undulating, and there is associated hemorrhage. The corpus luteum produces progesterone until (and if) the placenta takes over. If there is no pregnancy, it involutes.
(a) Hemorrhagic corpus luteum , with undulating layers of luteinized granulosa cells (arrow) and associated blood. (b) A corpus albicans , the remnant of a prior corpus luteum.
Corpus albicans : the former corpus luteum ultimately hyalinizes to form cloud-shaped pink islands in the ovary, the scars of old follicles (Figure 15.2).
Walthard rests : benign nests of transitional (urothelial)-type epithelium in the ovary and fallopian tube.
Rete ovarii : analogous to the rete testis, rete ovarii are rudimentary gland spaces located in the hilum of the ovary. They are angulated, slit-like spaces with a low cuboidal epithelium (Figure 15.3). Do not mistake them for cancer.
Rete ovarii . This vestigial structure is found at the hilum of the ovary, adjacent to large arteries (A) and veins. The rete consist of slit-like channels with a cuboidal cell lining (arrow).
Follicle cyst : a cyst lined with the normal components of the follicle, the granulosa cells, and the thecal layer (Figure 15.4). A similar lesion is the hemorrhagic corpus luteum cyst, which is a blood-filled corpus luteum.
Follicular cyst versus inclusion cyst . (a) A follicle cyst is lined by luteinized cells, similar to those seen in the corpus luteum (arrow). There is adjacent hemosiderin (oval). (b) An inclusion cyst may be lined by an attenuated epithelium, similar to the surface epithelium (arrow), or may show tubal metaplasia (arrowhead).
Inclusion cyst : a simple cyst lined with a cuboidal, columnar, or ciliated epithelium, often budding inward from the ovarian surface (Figure 15.4). When small, these can be called surface inclusion cysts. However, if they are large, they are best referred to as serous cystadenomas (see below).
For each cell type defined above (and then some), there are families of neoplasms that can arise. Table 15.1 lists the broad categories of neoplasms that occur in the ovary. Those in shaded boxes are rare enough that we will not talk about them here.
Neoplasms of the ovary.
Surface epithelial tumors
Germ cell tumors
Sex cord stromal
Granulosa cell tumor
Sertoli cell tumor
Leydig cell tumor
Sertoli–Leydig cell tumor
Epithelial neoplasms are by far the most common tumors of the ovary and come in three strengths: benign, borderline, and malignant. Benign tumors do not metastasize, malignant ones do, and borderline tumors may recur, spread intraperitoneally, or rarely metastasize. The nomenclature is as follows:
Adenoma : an adenoma is a benign epithelial proliferation. When cystic, as they often are, it is a cystadenoma . If biphasic with a secondary fibrous stromal component, it is an adenofibroma . If all three, it can be called a cystadenofibroma . Histologically, the cystadenomas are simple or multilocular cysts with a simple monolayered epithelial lining.
Borderline tumor (atypical proliferative tumor) : borderline lesions have an increasing epithelial complexity over the adenomas. Their epithelium begins to ruffle up in papillary fronds and may “ruffle down” into the stroma in a way that looks similar to invasion. However, they do not cross the basement membrane, do not invade the stroma, and do not induce a desmoplastic reaction. Serous borderline tumors can shed cells into the peritoneum, which may stick onto other organs and begin to grow. However, if they do not actually invade, they are called implants, not metastases. True invasion indicates a metastasis, not an implant.
Carcinoma : carcinomas commonly present as combination cystic/solid tumors. You may hear cystic tumors called cystadenocarcinomas , but there is not a significant clinical difference between calling something a carcinoma and a cystadenocarcinoma, so the latter term is falling out of use. These can be divided into low- and high-grade carcinomas, but all types can metastasize.
Carcinosarcoma : a carcinosarcoma is a carcinoma with a sarcomatous stroma—it is a true biphasic malignancy. In the gynecologic tract, these are also called malignant mixed Mullerian tumors or MMMT . An adenosarcoma would be a benign epithelial neoplasm in a sarcomatous stroma, which is rare.