Ovarian cancer can be divided into 3 major categories based on the type of cell from which it arises. This includes :
- Epithelial carcinoma
- Germ cell carcinoma
- Sex cord and stromal carcinoma
These are primary carcinomas of the ovary, which originate in the ovary itself.
The other type of carcinoma that may be found in the ovary is known as secondary or metastatic carcinoma. Here, the primary cancer is elsewhere in the body but it has metastasized to the ovary.
Different Types of Ovarian Cancer
Epithelial Ovarian Carcinoma
Epithelial ovarian carcinomas make up nearly 90% of all ovarian cancers. It occurs more frequently in older women and is derived from the surface epithelial cells of the ovary. It can be subdivided into :
- Serous carcinoma
- The ovarian serous cystadenocarcinoma is the most common malignant tumor of the ovary and accounts for about 35 to 50% of epithelial tumors.
- These tumors are usually bilateral (occurring in both the ovaries) and in most cases have spread beyond the ovaries at the time of diagnosis.
- Mucinous carcinoma
- These are the second most common type of epithelial tumors (10 to 20%).
- These tumors are usually unilateral (occurring in one ovary) and in some cases grow to a very large size.
- Pseudomyxoma peritonei is a rare condition that may develop as a result of accumulation of mucin in the abdomen due to slow leakage from the tumor. Although more common with mucinous tumors, it may also occur with serous cystadenomas. The outcome in these cases is usually poor.
- Endometrioid carcinoma
- This type of cancer may resemble endometrial adenocarcinoma of the uterus.
- It is more likely to be bilateral and may sometimes arise from a focus of endometriosis.
- In a large number of cases, endometrioid carcinoma may occur simultaneously with endometrial carcinoma of the uterus. This uterine cancer is usually a second primary carcinoma and not a metastatic cancer.
- Clear cell carcinoma
- This is also known as mesonephroid carcinoma of the ovary.
- It makes up about 5% of epithelial ovarian cancers.
- Transitional cell carcinoma
- The cells resemble transitional cell carcinoma of the bladder.
- Since this type of cancer is usually diagnosed late, the prognosis is poor when compared to other types of ovarian cancer.
- Undifferentiated carcinoma
- This accounts for less than 10% of epithelial cancers of the ovary.
- No specific cell type is distinguishable in this group.
Germ Cell Carcinoma
Germ cell cancers arise from cells that produce ova or eggs. This type of cancer occurs most commonly in young women and may have a better prognosis than epithelial tumors. The different types of germ cell cancers include :
- Dysgerminoma which is the most common type of germ cell carcinomas of the ovary, accounts for nearly 50% of such tumors. It is usually unilateral.
- Endodermal sinus tumor is the second most common germ cell carcinoma, occurring in about 20% of such cases. These tumors are very rapid growing, but are more likely to be unilateral.
- Immature teratomas make up about 20% of germ cell tumors.
- Embryonal carcinoma is a very rare form of germ cell carcinoma.
- Choriocarcinoma is also a rare germ cell tumor that is unrelated to pregnancy. It can be differentiated from gestational choriocarcinoma by having relatively lower elevations of hCG.
- Gonadoblastoma is another rare type of germ cell tumor, more common in the right ovary than in the left.
- Mixed germ cell tumors contain two or more germ cell elements and account for about 10% of germ cell carcinomas.
Sex Cord and Stromal Carcinoma
These tumors arise from connective tissue cells of the ovary. It may be subdivided into :
- Granulosa cell tumors are associated with excess estrogen production. They may cause precocious puberty in young girls and postmenopausal bleeding in older women.
- Sertoli-Leydig cell tumors usually causes some amount of virilization (masculinization) due to the secretion of the male sex hormone, testosterone. Often benign, it may be cancerous in some cases. If so, it is usually alow grade cancerous tumor.
Metastatic tumors may account for as many as 25% of all ovarian cancers. These are cancers that have spread to the ovary from primary sites in other parts of the body, most frequently from the breast, uterus, stomach, and colon. These tumors are usually bilateral and the signs and symptoms are similar to those of primary ovarian cancer. Carcinoma of the stomach that has metastasized to the ovary is known as Krukenberg tumor.