Etiology and pathogenesis of tumor growth
The development of any ovarian neoplasms, including epithelial forms, is closely associated with an unfavorable premorbid background. Primarily, this includes chronic inflammatory diseases of the uterine appendages. The leading factors triggering the pathological process are genetic mutations, as well as complex neurohumoral and endocrine disorders in the female body.
Tumor formation has a pronounced negative impact on reproductive health. The presence of such formations is directly associated with reduced reproductive function, primary or secondary infertility, and recurrent pregnancy loss. A crucial feature of pathogenesis is the fact that malignant neoplasms (cancer) often develop not primarily, but on the background of pre-existing benign ovarian tumors.
Principles of ovarian tumor classification
In modern gynecological practice, the WHO histological classification (1973) is used. It is based on a detailed microscopic characterization of tissues.
According to their cellular origin, all formations are divided into several large groups:
- Epithelial tumors (endometrioid, serous, and mucinous neoplasms belong specifically to this group).
- Sex cord-stromal tumors (including granulosa cell-stromal variants and androblastomas).
- Germ cell tumors (dysgerminomas and teratomas).
- Rare tumors.
- Tumor-like processes (non-neoplastic lesions).
Depending on the degree of malignant potential, absolutely benign, borderline (low malignant potential), and malignant variants are distinguished.
The place of endometrioid lesions among epithelial tumors
Endometrioid tumors are included in the clinical classification as one of the most common variants of surface epithelial-stromal ovarian lesions. This same broad group (cystadenomas, formerly called cystomas) includes:
- Serous tumors (simple smooth-walled and papillary).
- Mucinous tumors (pseudomucinous cystadenoma).
- Brenner tumors.
Serous cystadenomas account for the largest proportion of all benign epithelial neoplasms (up to 70%). Depending on the internal contents and the structure of the epithelial lining, they possess unique morphological features that must be differentiated from other types of cysts.
Characteristics of serous cystadenomas (as related epithelial tumors)
Since serous formations are the most frequent representatives of the epithelial group, their structure has been studied in the greatest detail.
Simple serous cystadenoma (smooth-walled cilioepithelial cystadenoma) is a true benign tumor. Macroscopically, it presents as a unilateral, unilocular ovoid formation with a smooth surface and tense-elastic consistency. Inside, there is clear, straw-colored serous fluid. The tumor is mobile, painless upon palpation in the posterior fornix, and rarely reaches large sizes. Malignancy occurs extremely rarely.
Microscopically, its outer surface is covered by low cuboidal epithelium, beneath which lies connective tissue stroma. The internal lining is formed by ciliated epithelium, which is prone to proliferation and resembles the epithelium of the fallopian tubes. With severe capsule stretching by fluid, this epithelium can flatten, lose cilia, disappear entirely, atrophy, or slough off, which greatly complicates differential diagnosis from ordinary functional cysts.
Papillary serous cystadenoma
This is a rarer morphological variety (about 7–8% of all ovarian tumors and 35% of all cystadenomas). Unlike the smooth-walled form, single or multiple dense whitish papillary vegetations on a broad base form on its inner surface.
The stroma of these papillae consists of small-cell fibrous tissue with a low number of epithelial cells and is prone to hyalinization. Layered calcifications—psammoma bodies—may form in the wall. The presence of such coarse papillae is a key diagnostic marker. They are found only in true tumors (serous cystadenomas) and never form in retention cysts. The detection of these structures during macroscopic examination of the resected specimen allows surgeons to exclude malignant growth with high probability.
Briefly: answers to topical questions
What macroscopic contents are characteristic of an endometrioid ovarian cyst?
An endometrioid ovarian cyst is characterized by thick, chocolate-brown hemorrhagic contents. In the early stages, pseudocysts are filled with a brownish mass. When foci coalesce, so-called "chocolate" cysts are formed, containing a thick, tar-like mass. The dark (purplish-bluish or brown) color is due to the accumulation of old blood inside the capsule. The internal surface of the formation also has a brown color.
What are the specific microscopic features of the endometrioid cyst wall structure?
Specific microscopic features include the presence of endometrial-type glands and hemosiderin deposits in the stroma.
- Epithelial lining—represented by columnar or cuboidal epithelium, which is frequently desquamated due to intracystic hemorrhages.
- Stroma—characterized by abundant vessels, the presence of hemorrhages of varying ages, as well as accumulations of hemosiderin and xanthoma cells.
What clinical symptoms are typical for an endometrioid ovarian cyst?
Typical manifestations may include dull, aching lower abdominal pain that intensifies during menstruation, infertility, abnormal uterine bleeding, and the presence of a pelvic mass. In the initial stages, the disease may be asymptomatic.
What instrumental diagnostic methods are used to confirm an endometrioid cyst?
Ultrasound examination, magnetic resonance imaging, and laparoscopy are used to confirm an endometrioid cyst.
- Transvaginal ultrasound (TVUS)—the baseline non-invasive method; cysts appear as formations with diffuse, low-level echo signals. Color Doppler mapping is applied.
- MRI (MRI)—a reserve method for solving complex diagnostic tasks.
- Laparoscopy—possesses the highest diagnostic value, allowing direct visual assessment of lesions and obtaining material for histological confirmation.
What are the main methods of surgical and conservative treatment for endometrioid ovarian cysts?
Treatment is combined; the leading role belongs to surgical treatment aimed at the maximal removal of endometrioid lesions. An argon beam coagulator or ultrasonic scalpel is used to remove lesions after prior biopsy. Hormonal therapy aims at ovulation suppression, induction of hypoestrogenemia and amenorrhea; progestogens, estrogen-progestogen drugs, gonadotropin-releasing hormone agonists, and antiprogestogens are used. Immunocorrection is used for widespread forms of the disease.
To memorize the main types of epithelial tumors (cystadenomas), use the acronym SMEB: Serous, Mucinous, Endometrioid, Brenner tumors.
Class and exam questions
Which group of tumors does an endometrioid cyst belong to?
According to the WHO histological classification, it belongs to the group of surface epithelial-stromal ovarian tumors.
What serves as the premorbid background for the development of ovarian tumors?
The primary background consists of chronic inflammatory diseases of the uterine appendages, as well as genetic, endocrine, and neurohumoral disorders.
How to distinguish a true papillary tumor from a retention cyst?
The most important criterion is the presence of coarse papillary outgrowths on the inner surface—they are characteristic only of true tumors (cystadenomas) and never occur in non-neoplastic cysts.
What is the risk of malignancy of a simple serous cystadenoma?
Transition into a malignant form (cancer) for smooth-walled serous cystadenoma is observed extremely rarely.
What else to study on this topic
- WHO Histological Classification of Ovarian Tumors (1973)
- Sex cord-stromal tumors (granulosa cell tumor, thecoma, fibroma)
- Germ cell neoplasms (dysgerminoma, mature and immature teratomas)
- Differential diagnosis of functional cysts and smooth-walled cystadenomas
- Morphological changes of the epithelium during stretching of the cyst capsule
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