The squamocolumnar junction of the cervix is an area of active squamous cell proliferation. In childhood, this junction is located on the exposed vaginal portion of the cervix. At puberty, because of hormonal influence and possibly because of changes in the vaginal pH, the squamous margin begins to encroach on the single-layered, mucus-secreting epithelium, creating an area of metaplasia (transformation zone). Infection with HPV (see Prevention, below) may lead to cellular abnormalities, which over time may develop into squamous cell dysplasia or cancer. There are varying degrees of dysplasia (Table 18–5), defined by the degree of cellular atypia; all atypia must be observed and treated if persistent or worsening.
Table 18–5.Classification systems for Papanicolaou smears. |Favorite Table|Download (.pdf) Table 18–5. Classification systems for Papanicolaou smears.
|Numerical ||Dysplasia ||CIN ||Bethesda System |
|1 ||Benign ||Benign ||Normal |
|2 ||Benign with inflammation ||Benign with inflammation ||Normal, ASC-US |
|3 ||Mild dysplasia ||CIN I ||Low-grade SIL |
|3 ||Moderate dysplasia ||CIN II ||High-grade SIL |
|3 ||Severe dysplasia ||CIN III ||— |
|4 ||Carcinoma in situ ||— ||— |
|5 ||Invasive cancer ||Invasive cancer ||Invasive cancer |
There are no specific symptoms or signs of CIN. The presumptive diagnosis is made by cytologic screening of an asymptomatic population with no grossly visible cervical changes. All visible abnormal cervical lesions should be biopsied (Figure 18–5).
Erosion of the cervix due to cervical intraepithelial neoplasia (CIN), a precursor lesion to cervical cancer. (Public Health Image Library, CDC.)
A. Cytologic Examination (Papanicolaou Smear)
In immunocompetent women, cervical cancer screening should begin at age 21. The recommendation to start screening at age 21 years regardless of the age of onset of sexual intercourse is based on the very low incidence of cancer in younger women and the potential for adverse effects associated with treatment of young women with abnormal cytology screening results. In contrast to the high rate of infection with HPV in sexually active adolescents, invasive cervical cancer is very rare in women younger than age 21 years. The US Preventive Services Task Force (USPSTF) 2018 statement recommends screening for cervical cancer in women aged 21 to 65 years as follows: for women aged 21 to 29 years, screening with cytology (conventional [Papanicolaou smear] or liquid based) alone every 3 years; and for women aged 30 to 65 years, screening with cytology alone every 3 years, with high-risk HPV testing ...