Uterine leiomyoma: macroscopy and topography
The etiology of uterine fibroid development is not fully understood, but a direct link has been established with conditions characterized by excess estrogen. These neoplasms are localized predominantly in the body and fundus of the uterus, forming single or, in the vast majority of cases, multiple nodes. Tumor sizes can vary widely.
Macroscopically, a benign tumor is a round node with clear boundaries that reliably separate it from healthy myometrium tissue. On cross-section, the tissue has a grayish-white color and a characteristic fibrous structure. Depending on the relationship to the layers of the uterine wall, three main types of leiomyomas are distinguished:
- Submucosal nodes: develop in close connection with the mucous membrane. They are a frequent source of uterine bleeding. If the node is located in the area of the internal os, it can provoke uterine contractions, leading to the opening of the cervical canal and the extrusion ("birth") of the tumor into the vagina. Such nodes are particularly prone to rapid infection and necrosis.
- Subserosal leiomyomas: grow toward the serous membrane, connecting to the uterine body with a wide base or forming a thin feeding stalk. The presence of a stalk makes the node mobile, but creates a high risk of torsion, which inevitably leads to necrotic tissue changes.
- Intramural leiomyomas: form directly within the thickness of the muscular layer of the uterus.
Histological varieties of leiomyomas
The microscopic picture of smooth muscle tumors is diverse. The basic variant is simple leiomyoma (leiomyoma simplex), formed by bundles of smooth muscle cells running in different directions. The cells have broad eosinophilic cytoplasm and elongated monomorphic nuclei with delicate chromatin. Mitoses are absent or single. The stroma contains a varying amount of connective tissue; when it is abundant, it is referred to as fibromyoma.
Special histological variants:
- Cellular leiomyoma: characterized by a high density of small smooth muscle cells with scant cytoplasm and poor development of connective tissue.
- Epithelioid leiomyoma: macroscopically, it is a soft yellow node. It includes three subtypes: leiomyoblastoma (round cells with eccentric nuclei), clear cell (polygonal cells rich in glycogen), and plexiform (strands of small cells in a hyalinized stroma). Subtypes are often combined.
- Bizarre (atypical) leiomyoma: contains giant symplast-like cells with hyperchromatic nuclei and abundant granular cytoplasm. Despite nuclear atypia, atypical mitoses are not found.
- Mitotically active leiomyoma: characterized by increased proliferation (5–9 mitoses per 10 high-power fields) without signs of cellular atypia.
- Lipoleiomyoma: contains mature fat cells, rare, mostly seen in postmenopause.
Secondary pathological changes may develop inside the nodes: hyalinization, myxoid or mucoid degeneration, calcification, cystic and fatty transformation, necrosis, and hemorrhages.
Leiomyosarcoma: malignancy criteria
Leiomyosarcoma accounts for about 1% of all malignant neoplasms of the uterine body. A crucial feature of pathogenesis: the tumor usually arises primarily (de novo), rather than as a result of malignant transformation of a preceding benign fibroid.
Macroscopically, leiomyosarcoma appears as a poorly demarcated node of soft consistency. The cut surface is variegated, varying from gray-yellow to pink, with prominent foci of hemorrhage and necrosis.
Microscopically (including epithelioid and myxoid variants), large spindle-shaped cells with sharply atypical nuclei, coarse chromatin, and large nucleoli are determined. Multinucleated giant cells, scant collagen stroma, and significant invasion into the myometrium and vessels are encountered.
Key diagnostic criteria for sarcoma:
- Presence of $\ge$ 10 mitoses per 10 high-power fields.
- OR presence of $\ge$ 5 mitoses per 10 high-power fields combined with marked cellular atypia (including atypical mitoses).
The prognosis for leiomyosarcoma is unfavorable: the neoplasm metastasizes hematogenously early and frequently recurs. The five-year survival rate does not exceed 40%.
Endometriosis
Endometriosis (endometriosis) is a pathological process characterized by the formation of ectopic foci of tissue structurally similar to the endometrium, far beyond its normal location.
This disease occurs in 10–15% of women of reproductive age. In the overall structure of gynecological morbidity, endometriosis firmly occupies 3rd place, inferior to inflammatory diseases and uterine fibroids. Its prevalence is especially high among patients with infertility—the pathology is diagnosed in every second such patient.
Briefly: answers to topical questions
Which inflammatory diseases of the female genital organs are specific?
Specific inflammatory diseases of the female genital organs include sexually transmitted infections (STIs) and tuberculosis.
- Gonorrhea causes gonococcal urethritis, salpingitis, purulent endocervicitis, bartholinitis, and tubo-ovarian abscesses.
- Genital chlamydia leads to the development of vestibulitis, catarrhal bartholinitis, salpingo-oophoritis, and endometritis.
- Tuberculosis manifests as damage to the fallopian tubes (salpingitis).
What theories exist for the origin of endometriosis?
The origin of endometriosis is explained by several main theories, since the exact etiology of this multifactorial disease has not been established.
- Implantation theory (retrograde menstruation theory) — movement of the endometrium through the fallopian tubes into the abdominal cavity during menstruation with subsequent implantation.
- Metaplastic theory — transformation of various tissues (coelomic epithelium, peritoneal mesothelium) into endometrium-like tissue.
- Embryonic theory (dysontogenetic) — formation of tissue from abnormally located embryonic remnants of the Müllerian duct.
- Dyshormonal theory — development of pathology against the background of hormonal disorders.
- Immune balance disruption theory — failure of mechanisms destroying ectopic cells by macrophages and NK cells.
What types of endometritis are distinguished by the nature of the course and morphological picture?
According to the nature of the course, acute and chronic endometritis are distinguished, which differ significantly in their morphological picture.
| Type of endometritis | Morphological picture |
|---|---|
| Acute endometritis | Infiltration of the mucous membrane by polymorphonuclear leukocytes. The process is often accompanied by massive tissue necrosis. |
| Chronic endometritis | Lymphomacrophage infiltration of endometrial tissue, presence of plasma cells, as well as sclerosis of the stroma and vessel walls. |
For the differential diagnosis of uterine sarcoma, remember the "Rule of Tens": malignancy is confirmed if 10 mitoses per 10 high-power fields are found.
Class and exam questions
How to distinguish cellular or mitotically active leiomyoma from leiomyosarcoma?
In benign leiomyomas, despite high cell density or the presence of 5–9 mitoses, signs of cellular atypia, atypical mitoses, and foci of coagulative necrosis are completely absent.
What clinical complication is characteristic of submucosal leiomyomas?
When located in the area of the internal os, they provoke uterine contractions, which can lead to the opening of the cervical canal and the "birth" of the tumor into the vagina.
Does leiomyosarcoma develop from a pre-existing benign myoma?
In the absolute majority of cases, leiomyosarcoma arises de novo, that is, primarily, and is not associated with the transformation of benign myomatous nodes.
What else to study on this topic
- Macroscopic differences between simple and epithelioid leiomyoma
- Mechanisms of secondary dystrophic changes in myomatous nodes
- Histological structure of plexiform and clear cell leiomyoma
- Methodology for counting mitotic figures in the differential diagnosis of smooth muscle tumors
- Pathogenesis of infertility in the development of endometriosis foci
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