Classification of Dysplasia
Dysplasia refers to a loss of the normal cytoplasmic differentiation or maturation that occurs with progression from the basal cell to the superficial keratinocyte in the cervical epithelium. The area of development of dysplasia and squamous cell cervical cancers is at the junction of the squamous and columnar epithelia (Fig. 2), and this area is evidently most susceptible to viral infection. The location of this junction, termed the transformation zone, is dynamic and responds to changes in vaginal pH in response to fluctuating estrogen levels. Increases in estrogen stimulation result in advancement of the columnar epithelium toward the vagina, and decreases in estrogen stimulation are followed by "retreat" of columnar epithelium into the endocervical canal. Columnar epithelium extending onto the ectocervix is called ectropion and is commonly seen during conditions of increased estrogen levels (i.e., during pregnancy, in women taking oral contraceptives, and in newborns). In contrast, it is unusual to see columnar epithelium on the ectocervix of a postmenopausal or premenarchal patient.
Figure 2. Colposcopic photograph of a normal cervix showing the squamocolumnar junction with metaplastic changes.
In 1988, the National Cancer Institute introduced the Bethesda Classification System for Pap smears (Table II).This system changed the nomenclature for dysplasia, reflecting advances in understanding cervical dysplasia. Other systems continue to be used, however, and are often listed sequentially in Pap smear reports (e.g., "LSIL, CIN1, mild dysplasia, HPV changes. . ."). Dysplasia is graded by the extent of epithelial abnormality (Table III). Low-grade squamous intraepithelial neoplasia (LSIL) is defined as mildly dysplastic cells or those with koilocytosis, whereas high-grade squamous intraepithelial neoplasia (HSIL) is defined as moderately or severely dysplastic cells.
The Bethesda System assigns a category for smears in which the cells have abnormal features that quantitatively or qualitatively fall short of dysplasia, termed ASCUS (atypical squamous cells of uncertain significance). In the recent revision of the Bethesda system, ASCUS is further classified as favoring reactive/benign processes or favoring dysplasia. Preliminary studies show that the majority of HSIL lesions fall into the latter category. (See box, "Common Questions About Pap Smear Screening.")
Medscape General Medicine. 1996;1(1) © 1996
Cite this: Management of Abnormal Cervical/Vaginal Pap Smears - Medscape - Mar 29, 1996.