Pathological changes of the cervix of the uterus are reflected in the clinico-morphological classification, the most widely used in practice:
- non-neoplastic processes: true erosion, cervical ectopia, ecropion, leukoplakia (simple), cervical polyps;
- precancerous changes (dysplasia) – cervical intraepithelial neoplasia (Cervical Intraepithelial Neoplasia – CIN);
The frequency of non-neoplastic (background) and precancerous processes of the cervix is very high and has no tendency to decrease. A large contingent of young women is subject to these diseases, which often affects their reproductive health.
The pathogenesis of cervical disease is to a large extent determined by its morphofunctional features. On the cervix there are two types of epithelium: the vaginal portion is covered with stratified flat, and the cervical canal is lined with a single-row cylindrical epithelium. Epithelial cells are separated from the stroma by a basement membrane containing reticulin, argyrophil fibers, collagen, neutral mucopolysaccharides. The stroma is represented by interlacing bundles of elastic, collagen fibers, contains blood and lymphatic vessels.
Stratified squamous epithelium consists of cells that differ in size, nuclear-cytoplasmic ratio, functional and mitotic abilities. The basal, parabasal, intermediate and surface layers are distinguished.
• The basal layer consists of a single row of immature cells with high mitotic activity (large cells with a large nucleus), here are reserve cells with bipotent properties (during regeneration they form both multi-layered squamous epithelium and cylindrical epithelium).
• Parabasal immature cells are located in 2-4 rows, also have a fairly large size, nucleus and mitotic activity.
• Intermediate cells have a polygonal shape, the inclusion of glycogen in the cytoplasm and are located in 6-12 layers. The number of layers of intermediate cells and the activity of glycogen accumulation are estrogen-dependent; they are greatest at reproductive age, minimal – with hypoestrogenism in the neutral period in girls, as well as in postmenopausal women.
• Superficial cells have a flattened navicular shape, a karyopyknotic nucleus, their cytoplasm is rich in glycogen, the number of rows of superficial cells varies depending on the phase of the menstrual cycle and can reach 12-18.In postmenopause, stratified squamous epithelium of the vagina and cervix is normally represented only by basal and parabasal cells.
The cylindrical epithelium is represented by one row of cylindrical, or goblet-shaped, cells with basally-spaced rounded nuclei. The cells of the cylindrical epithelium have low (compared to the basal cells of the stratified squamous epithelium) mitotic activity, they are able to produce mucopolysaccharides, resulting in the formation of a mucous plug in the cervical canal.
The border of the cylindrical and squamous epithelium has always attracted the attention of clinicians, since in 90% of cases of cervical disease arise in this particular zone (the “storm zone”). The presence of a junction of two types of epithelium in the vaginal portion of the cervix is regarded as a physiological process in girls and adolescents, in women during pregnancy. At reproductive age, the boundary between the cylindrical and flat epithelium is located in the area of the external os, the postmenopausal disease is on a different level in the cervical canal. The location of the border of the cylindrical and stratified squamous epithelium must be considered when examining and treating patients.