CERVICAL INTRAEPITHELIAL NEOPLASIA
ESSENTIALS OF DIAGNOSIS
The cervix often appears grossly normal.
Infection with the human papillomavirus is present.
Dysplastic or carcinoma in situ cells are noted in a cytologic test preparation (traditional Pap smear or liquid-based cytology).
Colposcopic examination reveals an atypical transformation zone with thickened acetowhite epithelium, coarse punctate, or mosaic patterns of surface capillaries.
Iodine-nonstaining (Schiller-positive) area of squamous epithelium is typical.
Biopsy diagnosis of cervical intraepithelial neoplasia (dysplasia or carcinoma in situ).
Lower genital tract squamous intraepithelial neoplasia is often multicentric (ie, affecting multiple anatomic sites that embryologically are derived from the same anogenital epithelium): cervical intraepithelial neoplasia (CIN), vaginal intraepithelial neoplasia (VAIN; see Chapter 49), vulvar intraepithelial neoplasia (VIN; see Chapter 49), and perianal intraepithelial neoplasia (PAIN). Approximately 10% of women with CIN have concomitant preinvasive neoplasia of the vulva, vagina, or anus. Conversely, 40–60% of patients with VIN or VAIN have synchronous or metachronous CIN.
In 2012, changes to this terminology were proposed in the Lower Anogenital Squamous Terminology (LAST) project of the College of American Pathology, where histologic results are described using the same terminology as cytologic results: CIN I is referred to as a low-grade squamous intraepithelial lesion (LSIL). CIN II is subdivided according to p16 staining. If p16 negative, CIN II is classified as LSIL; if p16 positive, CIN II is classified as a high-grade squamous intraepithelial lesion (HSIL). CIN III is referred to as HSIL. In this chapter, we will continue to use CIN terminology for histologic results because this terminology is used in the American Society of Colposcopy and Cervical Pathology guidelines.
CIN, formerly called dysplasia, means disordered growth and development of the epithelial lining of the cervix. There are various degrees of CIN. Mild dysplasia, or CIN I, is defined as disordered growth of the lower third of the epithelial lining. Abnormal maturation of the lower two-thirds of the lining is called moderate dysplasia, or CIN II. Severe dysplasia, CIN III, encompasses more than two-thirds of the epithelial thickness, with carcinoma in situ (CIS) representing full-thickness dysmaturity. While histologically evaluated lesions are characterized using the CIN nomenclature, cytologic tests are classified according to the Bethesda System, which was most recently revised in 2014. Briefly, atypical squamous cells are divided into those of undetermined significance (ASC-US) and those in which a high-grade lesion cannot be excluded (ASC-H). LSIL encompasses cytologic changes consistent with koilocytic atypia or CIN I. HSIL denotes the cytologic findings corresponding to CIN II and CIN III. Glandular cell abnormalities are categorized as atypical glandular cells not otherwise specified (AGC-NOS) or that favor neoplasia (AGC-FN), endocervical adenocarcinoma in situ, or adenocarcinoma. CIN may be suspected because of an abnormal cytologic test, but the diagnosis is established by cervical biopsy. Spontaneous regression, especially of CIN I, occurs in a significant number of patients, allowing for expectant management with serial cytologic tests ...