Cervical intraepithelial neoplasia (CIN) grading is determined by the proportion of dysplastic cells from the basal layer upward. CIN 3 is distinguished from CIN 2 by which histological criterion?

• A Dysplasia confined to the lower one-third of the epithelium
• B Full-thickness epithelial dysplasia with no surface maturation (or dysplasia involving upper two-thirds of epithelial thickness) ✓
• C Koilocytic change limited to the upper layers without basal involvement
• D Stromal invasion beyond the epithelial basement membrane

Explanation

CIN grading: CIN 1 = dysplasia in lower 1/3; CIN 2 = lower 1/2 to 2/3; CIN 3 (carcinoma in situ) = full-thickness or upper 2/3+ involvement with no surface maturation, marked nuclear atypia, and loss of polarity throughout. Stromal invasion beyond the basement membrane defines invasive carcinoma, not CIN. Koilocytes (perinuclear halos) reflect HPV cytopathic effect and may be seen in CIN 1/2.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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