PMC

The metaplastic process in the cervix begins with individual reserve cell proliferation: cytoplasmic cytokeratin (CK) 17 staining of subcolumnar cells (a) and nuclear p63 staining (b) Early immature metaplasia shows linear CK17 staining (c) which progresses to full-thickness staining in immature metaplasia (d,e) The preserved columnar endocervical cells are negative. As the metaplasia matures it becomes negative for CK19 with occasional retained basal keratinocyte staining (f).

Cervical intraepithelial neoplasia (CIN) III with p16+ (a) and cytokeratin (CK) 17– (b) surface epithelium. Only metaplastic cells in a gland beneath the dysplastic surface epithelium stain positive for CK17 (c) p63 immunoreactive nuclei of the dysplastic epithelium (d) In lesions of CIN II, antibody to p16 shows near full-thickness positivity (e), while antibody to CK17 reacts only with the metaplastic epithelium pushed above the dysplastic proliferation (f) There is typically a sharp line between metaplastic and dysplastic epithelium: p16+ dysplastic epithelium (g) and CK17 immunoreactivity (h)

Two examples of squamous lesions signed out as atypical immature metaplasia. A cervical biopsy specimen of a 32-year-old woman (a–c) revealing a flat squamous lesion several cell layers thick with disorderly stratification and nuclear enlargement (a). In step sections, the dysplastic features become more prominent and p16 stains strongly positive (b), while cytokeratin (CK) 17 is largely negative (c). Another cervical biospy of a 40-year-old woman (d–f) shows a squamous lesion involving an endocervical gland. p63 highlights the nuclei of basal and suprabasal cells (d), while p16 (e) shows strong uniform positivity of the entire stratified epithelium and CK17 stains the basal proliferating cells (f).