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Normal colposcopic findings
Original squamous epithelium
Squamous epithelium is the main histological type of epithelium lining the female lower genital organs (exocervix, vagina and vulva). It is composed of squamous cells arranged in four distinct layers, known as basal, parabasal (suprabasal), intermediate and superficial layers. Squamous epithelium is approximately 0.5mm thick, almost flat and colposcopically appears as pink, flat surface. Pale pink color is the result of the light reflected from small stromal vessels situated below epithelium.
Mature squamous epithelium
Mature, differentiated epithelum has low content of proteins and high content of glycogen. These two features are the basis of biochemical reactions developing after the application of 3-5% Acetic acid and Lugol's solution (Schiller's test): proteins with acid produce white and glycogen with Iodine produce brown color.
Abnormal (neoplastic) epithelium which is undifferentiated, retains high content of proteins and does not contain glycogen. This is why it remains white after the application of both Acetic acid and Iodine solution.
Atrophic squamous epithelium
In postmenopausal period, due to low estrogen levels, normal squamous epithelium undergoes atrophic changes. It becomes thinner, pale and smooth. Blood vessels are usually more readily visible through the thin epithelium. Even gentle examination can cause trauma easily. It is seen as small erosions on the cervix or vagina or typical subepthelial petechial bleeding. Atrophic changes are reversible. The use of local hormonal therapy can improve the colposcopic and cytologic picture of atrophic epithelium.
Columnar epithelium
Columnar epithelium is the second main type of epithelium in the uterine cervix. The entire endocervical canal and the endocervical glands are covered by columnar epithelium. This epithelium is composed of a single layer of cells which actively produce mucus. Columnar epithelium is not flat, but undulated, which gives it dense, micro-papillary structure. Colposcopically, columnar epithelium is red, because stromal vessels are easily seen through the thin layer of cells. For its undulated surface columnar epithelium presents as grape-like; small bubbles are essentially the tops of small epithelial undulations (papillae).
In the endocervix, columnar epithelium forms deep invaginations into the stroma- crypts which are also known as endocervical clefts. Sometimes the term glands, is used for these clefts, although they do not have typical glandular structure. They are important because they also can be involved by the neoplastic process.
The presence of columnar endocervical epithelium on the exocervix is called Ectopy. In normal situation, the squamo-columnar junction (SCJ) is situated at the external opening, whereas in Ectopy, the SCJ is located outside the external opening, on the exocervical site.
Ectopy is extremely common among women in adolescence and during pregnancy. The dynamic and physiological process of metaplasia gradually contributes to the fact that the SCJ moves higher towards the endocervix in parallel with the increasing age.
Deciduosis in pregnancy
The deciduosis or decidual reaction is the most specific histologic finding of the pregnant cervix. It is of great interest, because it creates colposcopic images that are totally unusual in gynecology. Decidual change is specific alteration in the cervical tissue (comprising collagen and elastin with a small amount of smooth muscle) affected by the action of progestagens. Although usually regarded as a hormonal response of the endometrial stroma, it can also be seen affecting the superficial stroma of the cervix. The change is usually quite focal, affecting only a small area of the cervix. It may be situated on the endocervix or ectocervix.
The cervical deciduosis presents as areas of edematous epithelial elevations which are visible on the ectocervix. Markedly bizarre changes can be present in this condition, and its appearance may be very suspicious of malignancy. The decidual changes of the cervix can appear as yellow, raised and friable lesions. Polypoid surface projections and an atypical vascular pattern contribute to altered morphological features.
Deciduosis may also present as doughnut rims to the gland openings, which, in cases of extreme change, may resemble "moon craters". These changes are caused by hypertrophy and hyperplasia of the cervical glandular tissue. Occasionally the decidual reaction may be quite extensive and may even get pseudopolypoid appearance referred to as "decidual polyp". This structure affects an area near the cervical os. It is usually yellowish and not covered with epithelium. It can also be a slightly haemorrhagic, showing atypical vessels. Colposcopic interpretation of this lesion is difficult.
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