Morphological picture and diagnostic criteria
A typical clinical example of the pathology's manifestation is the formation of cystic lesions in the reproductive system organs. The disease is frequently diagnosed in women of reproductive age (e.g., 35 years old) during surgical intervention to remove altered ovarian tissue.
A key step in establishing the diagnosis is the histological examination of the removed material. Pathoanatomical verification is based on three mandatory microscopic signs:
- Presence of a lining formed by endometrial-type epithelium;
- Formation of characteristic glandular structures;
- Presence of hemosiderin deposits in the stromal component, which serves as direct evidence of cyclic hemorrhages into the tissue.
Internal endometriosis of the uterine body
The pathological condition in which endometrioid heterotopias (areas of tissue identical to the endometrium) are located within the thickness of the uterine wall is called internal endometriosis, or adenomyosis. In this case, cells grow into the myometrium.
Pathological anatomy distinguishes three macroscopic forms of adenomyosis:
- Diffuse — uniform distribution of foci;
- Focal — local accumulations of glands;
- Nodular — formation of well-defined nodular elements.
Macroscopically, the uterus in adenomyosis is significantly enlarged. On cross-section, marked hyperplasia of the muscular layer is visualized, within the thickness of which specific cystic cavities filled with hemorrhagic contents are determined.
External genital heterotopias
If the ectopic endometrium extends beyond the uterine body but remains within the reproductive system, it is referred to as external genital endometriosis.
The most frequent localization (up to 70% of all external lesion episodes) is the ovaries. Initially, heterotopias infiltrate the cortical layer of the organ, and in severe, widespread cases, they also involve the medulla. Visually, the foci appear as small red or white spots on the surface and within the tissue thickness. Over time, they transform into large endometrioid cysts (so-called "chocolate" cysts), which frequently affect both ovaries simultaneously.
The second most frequent site is the pelvic peritoneum. Preferred zones here include the uterosacral and rectouterine (Douglas) pouches, as well as the area of the uterosacral ligaments.
Other genital sites of involvement include:
- Interstitial segments of the fallopian tubes;
- Retrocervical area (retro-cervical endometriosis) — infiltration of the rectovaginal adipose tissue behind the cervix, accompanied by smoothing of the isthmus and involvement of the rectal wall;
- Vagina, vaginal part of the cervix, perineum, and tissues of the external genitalia;
- In deep infiltrative processes — rectovaginal septum, vaginal walls, and rectosigmoid colon.
Extragenital localizations and metastatic pathways
Endometrioid heterotopias possess a unique property of invasively growing into any adjacent tissues (peritoneum, intestinal wall, skin, ureter, urinary bladder). Furthermore, they are capable of disseminating like true tumor cells, using lymphogenic and hematogenous pathways to do so. This explains the extensive spectrum of affected zones.
Extragenital foci can form in the following structures:
- Digestive tract: appendix, small and sigmoid intestine;
- Urinary tract: urinary bladder and ureters;
- Respiratory system: lungs;
- Superficial structures: umbilicus, subcutaneous adipose tissue of the anterior abdominal wall, and postoperative scars (e.g., following laparotomy).
Upon realization of the lymphogenic metastatic pathway, pathological foci are detected in regional lymph nodes. The rarest and most distant localizations resulting from hematogenous dissemination are ocular structures, specifically the conjunctiva.
To memorize the forms of adenomyosis, use the acronym DFN: Diffuse, Focal, Nodular. To understand the pathways of spread, remember that heterotopias behave like a tumor: they are capable of growing by contact, as well as metastasizing via lymphogenic and hematogenous routes.
Class and exam questions
What is the main difference between adenomyosis and external endometriosis?
Adenomyosis is an internal endometriosis in which foci affect exclusively the uterine body, growing into the myometrium. All other localizations within the small pelvis belong to the external process.
Which microscopic signs are strictly mandatory to confirm the diagnosis?
The diagnosis is established upon detecting glandular structures lined with endometrial-type epithelium in the stroma, as well as accumulations of hemosiderin indicating old hemorrhages.
Can endometrioid tissue affect distant organs?
Yes, due to the capacity for lymphogenic and hematogenous metastasis, heterotopias can be detected in the lungs, lymph nodes, and even on the ocular conjunctiva.
What else to study on this topic
- Mechanisms of formation of endometrioid ("chocolate") cysts in the ovaries
- Pathogenesis and complications of deep infiltrative endometriosis
- Features of retrocervical endometriosis with rectal involvement
- Differential diagnosis of the nodular form of uterine adenomyosis
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