Uterine Leiomyoma: Macroscopy and Topography
The etiology of uterine myomas is not entirely clear, though a direct link with conditions exhibiting excess estrogen has been established. These neoplasms are localized predominantly in the body and fundus of the uterus, forming solitary or, in the vast majority of cases, multiple nodes. Tumor sizes vary widely.
Macroscopically, a benign tumor appears as a well-circumscribed, rounded node with distinct borders that clearly separate it from healthy myometrial tissue. On cross-section, the tissue is grayish-white with a characteristic whorled, fibrous structure. Based on their relationship to the layers of the uterine wall, three main types of leiomyomas are distinguished:
- Submucosal nodes: develop in close relation to the endometrium. They frequently present as a source of uterine bleeding. If a node is located near the internal os, it can provoke uterine contractions, leading to dilation of the cervical canal and extrusion («birth») of the tumor into the vagina. These nodes are especially prone to rapid infection and necrosis.
- Subserosal leiomyomas: grow toward the serosal surface, attaching to the uterine body via a broad base or forming a slender feeding stalk. The presence of a stalk makes the node mobile but creates a high risk of torsion, inevitably leading to ischemic necrosis.
- Intramural leiomyomas: develop directly within the thickness of the myometrium.
Histological Varieties of Leiomyomas
The microscopic appearance of smooth muscle tumors is diverse. The baseline variant is the simple leiomyoma (leiomyoma simplex), formed by intersecting fascicles of smooth muscle cells. The cells possess broad eosinophilic cytoplasm and elongated monomorphic nuclei with delicate chromatin. Mitoses are absent or rare. The stroma contains varying amounts of connective tissue; an abundance of this tissue warrants the term fibromyoma.
Special histological variants include:
- Cellular leiomyoma: characterized by a high density of small smooth muscle cells with scant cytoplasm and minimal connective tissue.
- Epithelioid leiomyoma: macroscopically a soft, yellow node. It includes three subtypes: leiomyoblastoma (rounded cells with eccentric nuclei), clear cell (polygonal cells rich in glycogen), and plexiform (cords of small cells in a hyalinized stroma). Subtypes frequently combine.
- Bizarre (atypical) leiomyoma: contains giant symplasts-like cells with hyperchromatic nuclei and abundant granular cytoplasm. Despite nuclear atypia, atypical mitotic figures are absent.
- Mitotically active leiomyoma: exhibits increased proliferation (5–9 mitoses per 10 high-power fields) without features of cellular atypia.
- Lipoleiomyoma: contains mature fat cells, is rare, and occurs primarily in postmenopausal women.
Secondary pathological changes may develop within the nodes: hyalinization, myxoid or mucoid degeneration, calcification, cystic and fatty transformation, necrosis, and hemorrhage.
Leiomyosarcoma: Criteria for Malignancy
Leiomyosarcoma accounts for about 1% of all malignant neoplasms of the uterine corpus. A crucial pathogenetic feature is that the tumor typically arises primarily (de novo), rather than via malignant transformation of a pre-existing benign myoma.
Macroscopically, leiomyosarcoma appears as a poorly demarcated, soft-consistency node. The cut surface is variegated, ranging from gray-yellow to pink, with pronounced foci of hemorrhage and necrosis.
Microscopically (including epithelioid and myxoid variants), large spindle-shaped cells with markedly atypical nuclei, coarse chromatin, and prominent nucleoli are identified. Multinucleated giant cells, sparse collagenous stroma, and significant invasion into the myometrium and blood vessels are observed.
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 mitotic figures).
The prognosis for leiomyosarcoma is unfavorable: the neoplasm early gives hematogenous metastases and frequently recurs. The 5-year survival rate does not exceed 40%.
Endometriosis
Endometriosis (endometriosis) is a pathological process characterized by the presence of ectopic foci of tissue structurally and functionally analogous to the endometrium far outside its normal anatomical location.
This disease occurs in 10–15% of women of reproductive age. In the overall structure of gynecological morbidity, endometriosis firmly occupies 3rd place, second only to inflammatory diseases and uterine myomas. Its prevalence is especially high among infertile patients, where the pathology is diagnosed in every second such patient.