Ovarian tissue composition is very complex and is the organ with the highest number of primary tumor types in all organs of the body. The histological structure and biological behavior of different types of ovarian tumors are very different and are crucial for the treatment and prognosis of tumors.
[Histological classification].
The histologic classification of ovarian tumors developed by the World Health Organization (WH0, 1973) is the commonly used classification of ovarian tumors at present. The main types are: epithelial tumors, germ cell tumors, interstitial tumors of the sex cords, other types and metastatic tumors.
1. Epithelial tumors account for 50% to 70% of primary ovarian tumors, and their malignant types account for 85% to 90% of ovarian malignant tumors. The tumors originate from the germinating epithelium on the ovarian surface and have the potential to differentiate into various mullerian epithelium. The tumors differentiate to fallopian tube epithelium to form plasmacytoma, to cervical mucosa to form mucinous tumor, and to endometrium to form endometrium-like tumor.
2.Germ cell tumors, accounting for 20% to 40% of ovarian tumors. Germ cells are derived from endodermal tissues other than gonads and have the function of generating multiple tissues. The undifferentiated ones are asexual cell tumors, the embryonic pluripotent ones are embryonal carcinomas, the differentiation to embryonic structure is teratoma, the differentiation to extra-embryonic structure is endodermal rustic tumor and choriocarcinoma.
3.Interstitial tumor of the sex cords, accounting for about 5% of ovarian tumors. Interstitial tumors of the sex cord originate from the mesenchymal tissue of the primitive body cavity and can differentiate into both sexes. It can differentiate to both sexes and form granulosa cell tumor or supportive cell tumor to the epithelium, and follicular membrane cell tumor or mesenchymal cell tumor to the mesenchyme. These tumors often have endocrine function and are also called functional ovarian tumors.
4. Metastatic tumors account for 5% to l0% of ovarian tumors, and their primary sites are mostly in the gastrointestinal tract, breast and reproductive organs.
Pathology
1. Ovarian epithelial tumor is the most common ovarian tumor. They are mostly seen in middle-aged and elderly women. Ovarian epithelial tumors are divided into benign, junctional and malignant. Junctional tumor refers to active epithelial cell proliferation and nuclear heterotypes, increased nuclear division phase, which shows an increase in epithelial cell levels but no mesenchymal infiltration, and is a kind of low potential malignant tumor. In contrast, ovarian epithelial carcinoma develops rapidly, is not easily diagnosed early, is difficult to treat and has a high mortality rate.
(1) Plasmacytoma.
Plasmacytoid cystadenoma: It accounts for about 25% of benign ovarian tumors. The tumor is mostly unilateral, with smooth surface, cystic, thin wall, and filled with yellowish clear liquid. Microscopically, the wall of the cyst is fibrous connective tissue with a single layer of columnar epithelium and thick papillary branches.
Intersecting plasmacytic cystadenoma: medium sized, mostly bilateral. Papillary growth is less frequent inside the capsule and more often grows outside the capsule. Microscopically, the papillary branches are slender, the nuclei are mildly heterogeneous, the nuclear schizophrenic phase is <1/HP, there is no interstitial infiltration, and the prognosis is good.
Plasmacytoid cystic adenocarcinoma: It accounts for about 40% to 50% of ovarian malignant tumors. It is mostly bilateral, large, semi-substantial, multi-housed, lumen filled with papillae, brittle, and cloudy cystic fluid. Microscopically, the epithelium of the cyst wall is obviously hyperplastic, with obvious cellular heterotypes and infiltration into the interstitium.
(2) Mucinous tumors.
Mucinous cystadenoma: accounts for 20% of benign ovarian tumors. They are mostly unilateral and large in size. The surface is smooth and the cut surface is multi-roomed and filled with jelly-like mucus. There are few papillary growths in the capsule, which can occasionally pierce on their own. The malignancy rate is 5% to l0%. Microscopically, the cyst wall is fibrous connective tissue lined with a single layer of columnar epithelium.
Intersecting mucinous cystadenoma: generally large, rarely bilateral, with smooth surface and often multi-roomed. The cystic wall is thickened with parenchymal areas and papillae formation with tiny papillae. Microscopically, cells are seen to be mildly heterogeneous, with protrusion of proliferating epithelium into the lumen forming short thick papillae without interstitial infiltration.
Mucinous cystic adenocarcinoma: It accounts for l0% of malignant tumors. It is unilateral and large, with papillae or parenchymal areas visible in the cyst wall, cystic and solid in the cut surface, and cloudy or bloody cystic fluid. Microscopically, dense glands with obvious cellular heterogeneity and interstitial infiltration are seen. The prognosis is better than that of plasmacytoid cystic adenocarcinoma.
(3) Ovarian endometrioid tumor.
Benign ovarian endometrioid tumors are relatively rare. They are single-compartment, with smooth surface and cystic wall lined with a single layer of columnar epithelium, resembling normal endometrium. Interdigitating tumors are rare. The malignant ones are endometrioid carcinoma of the ovary, accounting for about l0% to 24% of primary ovarian malignant tumors. The tumors are unilateral and numerous, cystic or solid with papillary growth and hemorrhagic cyst fluid. The microscopic features are very similar to endometrial carcinoma, which is often complicated by endometrial cancer.
(4) Clear cell tumor.
It originates from the epithelium of Mullerian duct and is benign and rare. It is rare and benign. Intersectional cases are often combined with clear cell carcinoma. Clear cell carcinoma accounts for 5%-ll% of ovarian cancer. It is often combined with endometriosis and is cystic, unilateral and large. Microscopically, the tumor cells have obvious nuclear heterogeneity and deep staining, with special bootstrap cells attached to the capsule.
2. Ovarian germ cell tumors.
The incidence is second only to epithelial tumors and is more common in children and adolescents.
(1) Teratoma: A tumor composed of polyembryonic tissue structure, occasionally containing one embryonic component. Most of the tumor tissues are mature and a few are immature.
Mature teratoma: It is benign and accounts for 85%-97% of germ cell tumors. They can occur at any age, with the majority being between 20 and 40 years old. Most of them are unilateral, medium-sized, round or ovoid, with smooth and tough walls. The cavity is filled with oil and hair, and sometimes teeth or bone are visible. The wall of the cyst is often raised in a small mound-like protrusion into the cavity called the “head node”. Mature cystic teratoma has a malignant rate of 2% to 4%, mostly in postmenopausal women; the epithelium of the “head node” is prone to malignant transformation, forming squamous cell carcinoma, with poor prognosis.
Immature teratoma: It is a malignant tumor, accounting for 1% to 3% of ovarian teratoma. The tumor is composed of immature embryonic tissue with different degrees of differentiation, mainly primitive neural tissue. The tumors are solid in nature. The malignancy of the tumor depends on the proportion of immature tissue, the degree of differentiation and the neuroepithelial content.
(2) Anaplastic cell tumor: It is a solid tumor with moderate malignancy, which is usually found in adolescent and fertile women. The tumors are mostly unilateral, round or oval, medium-sized, solid, with smooth surface. Microscopically, large round or polygonal cells with large nuclei and abundant cytoplasm are seen, and the interstitium is often infiltrated by lymphocytes. It is particularly sensitive to radiotherapy.
(3) Yolk sac tumor: also known as endodermal sinus tumor. It is mostly seen in children and adolescents. The tumor is unilateral, large, round or ovoid. The tumor is partially cystic in cross-section, with many areas of hemorrhagic necrosis. Microscopically, lax reticular and endodermal sinus-like structures are seen. The tumor cells produce alpha-fetoprotein, so the patient’s serum AFP concentration is high, and its concentration correlates with tumor growth and is an important marker in diagnosis and treatment monitoring. The tumor grows rapidly, is prone to early metastasis and has poor prognosis.
(4) Choriocarcinoma: Primary choriocarcinoma, also known as non-pregnant choriocarcinoma of the ovary, is a highly malignant ovarian tumor that develops from multipotential cells in ovarian germ cells to extraembryonic structures. It is often combined with other malignant germ cell tumors. Gestational choriocarcinoma is usually not combined with other malignant germ cell tumors. Typically, the tumor is large, unilateral, solid, soft, and with marked hemorrhagic necrosis. The microscopic morphology is like that of uterine choriocarcinoma, consisting of cytotrophoblasts and syncytial trophoblasts. The prognosis of non-pregnant choriocarcinoma is worse than that of gestational choriocarcinoma, with poor therapeutic effect and death within a short period of time.
3. Interstitial tumor of ovarian gonads
They originate from the gonadal cords and interstitial tissues in the primitive gonads and account for 4.3%-6% of ovarian tumors. Tumors can be formed by a single cell or a combination of different cellular components. Many types of interstitial tumors of the gonads can secrete steroid hormones and show symptoms of endocrine disorders.
(1) Granulosa cell tumor: It is a low-grade malignant tumor with a peak age of 45 to 55 years. It can secrete estrogen, so it has feminization effect. Pseudo-precocious puberty may occur before puberty, and menstrual disorders may occur in patients of reproductive age, while postmenopausal patients may have irregular vaginal bleeding, often combined with endometrial hyperplasia and even endometrial adenocarcinoma. The tumor is mostly unilateral, lobulated, with smooth, solid or partially cystic surface and brittle and soft tissue on the cut surface with foci of hemorrhagic necrosis. Microscopically, granulocytes are seen surrounded by small round cystic cavities with eosinophilic material and nuclear fragments (Call-Exner vesicles) in the center.
(2) Follicular meningioma: It is a solid tumor of the ovary with endocrine function, which can secrete estrogen and has a feminizing effect. They are often found in combination with granulosa cell tumors. Pure follicular membranous cell tumor is a benign tumor, unilateral, covered with a glossy fibrous envelope. It is solid and grayish in color. Microscopically, the tumor cells are short spindle-shaped with interlocking cells arranged in a swirling pattern. It is often combined with endometrial hyperplasia. Malignant follicular meningioma is rare.
(3) Fibroma: It is a relatively common benign tumor, accounting for 2% to 5% of ovarian tumors. They are mostly seen in middle-aged women, mostly unilateral, of medium size, with smooth surface, grayish-white cut surface, solid and hard. Microscopically, spindle-shaped tumor cells are seen, arranged in a woven pattern. Occasionally, patients with pleural fluid or ascites are seen, which is called Menges syndrome.
4.Metastatic tumor of ovary
Primary cancer of any site may metastasize to the ovary. Common primary tumor organs include breast, stomach, intestine, genital tract, urinary tract, etc., accounting for 5% to l0% of ovarian tumors. Kuchenberg’s tumor is a metastatic adenocarcinoma with the primary site in the gastrointestinal tract. The tumor is bilateral, of medium size, keeping the ovary intact or in a kidney shape. There are no adhesions, the cut surface is solid and colloid-like, mostly with ascites; microscopically, typical imprinted cells are seen, containing mucus, with poor prognosis.
WHO histological grading criteria: ① differentiation grade 1: highly differentiated; ② differentiation grade 2: moderately differentiated; ③ differentiation grade 3: poorly differentiated.