Premalignant Conditions of the Cervix: Cervical Intraepithelial Neoplasia

Premalignant Conditions of the Cervix: Cervical Intraepithelial Neoplasia

Definitions

Cervical intraepithelial neoplasia (CIN), or cervical dysplasia, is the presence of atypical cells within the squamous epithelium. These atypical cells are dyskaryotic, exhibiting larger nuclei with frequent mitoses. The severity of CIN is graded I–III and is dependent on the extent to which these cells are found in the epithelium (Fig. 4.3). CIN is therefore a histological diagnosis.

Fig. 4.3 The cervical epithelium and cervical intraepithelial neoplasia (CIN). (a) Normal cervical epithelium; proliferation in basal layer only with small nuclei. (b) CIN I–II: abnormal cells with larger nuclei proliferating in the lower one-third to two-thirds of the epithelium. © CIN III: abnormal cells occupying the entire epithelium. (d) Microinvasion: abnormal cells have penetrated the basement membrane.

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CIN I (Mild Dysplasia):

Atypical cells are found only in the lower third of the epithelium.

CIN II (Moderate Dysplasia):

Atypical cells are found in the lower two-thirds of the epithelium.

CIN III (Severe Dysplasia):

Atypical cells occupy the full thickness of the epithelium. This is carcinoma in situ; the cells are similar in appearance to those in malignant lesions, but there is no invasion. Malignancy ensues if these abnormal cells invade through the basement membrane.

If untreated, about one-third of women with CIN II/III will develop cervical cancer over the next 10 years. CIN I has the least malignant potential: it can progress to CIN II/III, but commonly regresses spontaneously