Colposcopy possibly has its greatest use in evaluating a patient with an abnormal papanicolaou test. Many patients with positive or doubtful papanicolaou smears exhibit no obvious target lesion on gross examination with the unaided eye. The challenge benefit of colposcopy is in its potential to help identify and localize with a high degree of accuracy lesions not visible by gross inspection. Directed biopsies of these targeted sites can then be taken.
Colposcopic examination ensures that biopsy specimens obtained in this way represent the most advanced histologic process present. Once one has located the areas of abnormality and identified the point of greatest cellular atypia by colposcopy, one can remove such loci in whole or in part under continued colposcopic guidance. This can be accomplished usually in an office setting and without anesthesia. The colposcopically directed biopsy has supplanted some less reliable techniques for localizing atypical lesions. The false negative rate of multiple blind biopsies from nonstaining areas approaches three to eight percent. Cytology, although a practical aid in mass screening for cancer, is obviously of little or no help in pinpointing or delimiting a lesion. The advent of colposcopy directed biopsies has obviated the need for at least eighty percent of diagnostic cervical conizations. Although cold knife conization is generally considered a minor surgical procedure, it is not innocuous. Serious complications may result, such as hemorrhage, infection, and infertility.
Colposcopy has successfully substituted the safety of the office procedure of directed biopsy for many conizations. Complications of biopsy occur in fewer that point one percent of cases as contrasted with the ten percent rate of serious hemorrhage and one percent additional complications attributable to conization. The major reduction in cervical conization is of special importance for pregnant patients in whom such procedures are associated with much blood loss and frequent fetal wastage. Diagnostic conization in gravidas has been almost entirely eliminated because the squamocolumnar junction in pregnancy is so often everted well out onto the portion of the cervix. If the entire squamocolumnar junction and part of the endocervical canal are visible with the colposcope, and if the upper limits of any abnormal epithelium are seen, one can feel confident that the areas of maximum colposcopic change will be sampled and subjected to histologic examination, thus, all significant pathology can be diagnosed accurately. When the lesions lie wholly within the endocervical canal or extend out of view up into the canal, diagnostic conization is warranted. Since the squamocolumnar junction is visible in its entirely in more than ninety percent of all women, and all or part of the endocervical canal is visible in nearly seventy five percent, the need for diagnostic conization is infrequent.
Colposcopy permits one to delineate the outer limits of tumor on the cervix, vagina, and vulva, so that precise and adequate surgical margins can be achieved. When cervical conization is employed for treatment in a young patient with carcinoma in situ of the cervix, colposcopy can help to determine appropriate areas for surgical incisions. Approximately six percent of early cervical cancers have a cancerous focus or foci in the vaginal fornices as part of a multicentric growth. Colposcopy enables one to recognize these areas preoperatively. After hysterectomy for cervical or endometrial carcinoma, or subsequent to radiation therapy, follow up colposcopy can be used to investigate for the presence and precise location of early vaginal recurrence so that treatment can be carried out expeditiously.
Colposcopy is useful in determining the nature of benign disease. It helps to distinguish preclinical carcinoma from important conditions such as condylomata acuminate, papillomata, Trichomonas vaginalis vaginitis, all of which may give rise to abnormal cytology. In the presence of a negative papanicolaou smear, many benign changes are more readily diagnosed with colposcopy of benign lesions can therefore be avoided.
Serial colposcopy appears to be the most effective method for evaluating the epithelium of the vagina and the cervix in patients exposed utero to diethylstilbestrol. The benign condition of vaginal adenosis is observed with the colposcope in approximately ninety percent of diethylstilbestrol offspring. The potential for development of clear adenocarcinoma or squamous cell dysplasia of the vagina in these patients is the primary subject of concern. Foci of adenosis in the upper vagina of diethylstilbestrol exposed patients submucosal in location in sixty percent, and no exfoliation can be expected to occur in these cases. Thus, dysplatic or neoplastic transformation maybe undetected by cytology at least sixty percent of the time. Moreover, some cases of clear cell adenocarcinoma have demonstrated negative cytology. Hopefully, microscopic foci of invasive clear cell adenocarcinoma or preclinical squamous carcinoma will be detected with the colposcope long before they are visible to the naked eye. One anticipates that any changes in the morphology of the epithelium which are noted by serial colposcopy may signal the presence of malignant disease.
Colposcopy is valuable for teaching and clinical research. It has created a new dimension for students and clinicians to the understanding of the pathogenesis of neoplasia by proving a unique means of observing and evaluating tissue in the process of dynamic change. The coloscope enables the investigators to establish protocols for treatment of dysplastic and neoplastic lesions by local excision or local destruction by electrodiathermy or cryosurgery. Carbon dioxide laser treatments have been used on an experimental basis as a method for eradicating lesions of the cervix and vagina. Such lasers are constructed for use only when attached to a colposcope.
Histologic Basis of Colposcopy
Every colposcopic picture is the counterpart of a specific tissue pattern. Each tissue pattern, in return, is determined by the nature of its surface epithelium and associated connective tissue stroma. The colposcope produces its effect by illuminating both surface epithelium and underlying stroma. When a sheet of epithelium composed of a particular cell population is interposed between the colposcopic light source and subjacent stroma, a characteristic visual impression is created. The visual image observed is a reflection of epithelial cell number organization, and morphology. This image is also influenced by the vascular arrangement of the underlying stroma. Each of the many variations in stromal vascular architecture can be modified by a number of possible changes in epithelial cellular morphology. The various combinations of epithelium and stroma produce identifiable colposcopic images. Consequently, both normal and abnormal epithelia take on colposcopic appearances almost as characteristic as those seen on histologic examination. Each cervix and vagina is colposcopically unique. Variations in colposcopic appearances are manifested by changes in morphologic features such as color and opacity, vascular configuration, and surface contour. These features differentiate normal from atypical tissue and form the basis for all colposcopic examination.
Color and opacity are important indicators o the cell population of the epithelium. Native squamous epithelium is the term used to refer to the epithelial layer that usually lines the vagina and part of the cervical portion. It appears pink, translucent, and featureless under colposcopic examination. The incident light passes uniformly through several homogenous squamous cell layers to yield a uniform homogenous surface pattern.
Native columnar epithelium is the term used to refer to the tissue that lines the endocervical canal. Such tissue is sometimes present also on the exocervix around the anatomic external cervical os. It is composed of only a single layer of cells which overlies a highly vascular stroma. It is usually thrown up into folds. When illuminated by the colposcope, this tissue appears quite red as a result of the transparency of the columnar cells and proximity of the stromal capillary bed to the epithelial surface.
The red color is most pronounced when columnar tissue has first been washed with saline. Acetic acid creates the characteristic appearance of grape clusters because of the cellular edema which increases the surface opacity and tends to reduce the color contrast. Specific properties, such as epithelial height, cell density, nuclear atypia, cellular differentiation, and mucus or keratin production, alter the optical response. Any condition which exhibits hyperchromatic nuclei, diminished cytoplasm, or dense keratin accumulation reflects more light than normal tissue and therefore appears opaque or white under the colposcope. Inflammation can alter the color of the normal squamous epithelium by increasing vascularity, keratin production, and so forth.
Surface tissue comprised of fewer than normal squamous cell layers transmits more translucent than native squamous epithelium which is typically fifteen to twenty cell thicknesses. Postmenopausal squamous epithelium is especially pale because of a decrease in stromal vascularity along with a decrease in epithelial cell density and nuclear size. The thinness and relative colposcopic translucency of epithelium can be offset by the increased nuclear density of undifferentiated cells. A strip of epithelium which displays fewer than normal layers of cells with larger than normal nuclear size may create the same opaque colposcopic appearance as tissue which is composed of many cell layers and small nuclei. One of the principal advantages of colposcopy is its capability for evaluating surface and subepithelial vascular structure and spatial arrangement. This aspect of tissue analysis is virtually indiscernible by histologic sections.
Tissues which differ in cellular structure and activity show important differences in number, size, configuration, caliber, and disposition of their vessels. Variation in the vascular architecture of adjacent tissues permits clear distinction between physiologic and pathologic areas of vaginal and cervical epithelium. Specific types of terminal vessels are characteristics of the normal vaginal and cervical epithelia. Vessels within the villi of columnar epithelium are not easily delineated with a colposcope; columnar tissue appears uniformly red because of the delicate quality of the stromal vasculature which is located at the same uniform depth in all areas. Capillary patterns in the form of network of hairpin structures are basic to native squamous epithelium. When connective tissue papillae of the squamous epithelium of the cervix and vagina are poorly developed or absent, the stromal vasculature is flattened and everywhere equidistant from the tissue surface. Consequently, a meshwork or network of delicate capillaries is seen. Atrophic squamous epithelium, because it is especially translucent, sometimes displays spider like vessels beneath the network capillaries.
Hairpin capillaries are observed if stromal papillae are well developed in squamous epithelium. A hairpin vessel is formed by the ascending and descending branches of a capillary loop within a papilla. The extent of stromal papillation and the angle of observation determine whether or not such hairpin structures are seen in their entirety. Within the same colposcopic section, hairpin vessels can be viewed tangentially as crests of loops, or directly on end as fine punctuation vessels. Pathologic epithelia also demonstrate characteristics vascular patterns based on changes in vessel number, size, organization, intercapillary distance, and so forth. Alterations in surface contour reflect growth disorders of epithelium, specifically potential neoplasia.
The stereoscopic magnification provided by the colposcope lends itself to the effective study of the surface configurations. Native squamous epithelium has a smooth surface, whereas columnar epithelium has multiple grape-like papillomatous excrescences. The grapes or villi are most prominent at the distal end of the endocervical canal and often circumorally on the exposed exocervix. In situ and invasive carcinomas can both display raised and irregular surfaces, dysplasias rarely do. It should be emphasized that all colposcopic appearances are based on the morphologic criteria described. Each colposcopic pattern reflects its associated histologic structure. The visible portion of the female genital tract is covered by stratified squamous epithelium which lines the vagina and exocervix and simple columnar epithelium which lines the endocervical canal. The junction of these two tissue types can occur at various locations on the uterine cervix. The squamolumnar junction commonly coincides with the anatomic external cervical os. In postmenopausal females, it occurs frequently within the endocervical canal. Most menstruating females display this junction on the exposed exocervix. When this occurs, it is often mistakenly referred to as cervical eversion, ectropion, congenital erosion, or erythroplakia. It is present in many female fetuses. It occurs at the other times of life in exaggerated form in response to high estrogen stimuli, such as puberty, pregnancy, or oral contraceptives. In approximately four percent of the female population and in many women who were exposed to diethylstilbestrol in utero, the squamocolumnar junction may actually extend out onto the vaginal fornices or vaginal wall.