General
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• Most of cervix is composed of fibromuscular tissue
• Epithelium is either squamous or columnar
• Endocervix: lined by columnar epithelium that secretes mucus; epithelium has complex infoldings that resemble glands or clefts on cross section; mucosa rests on inconspicuous layer of reserve cells
• Ectocervix (exocervix): covered by nonkeratinizing, stratified squamous epithelium, either native or metaplastic; has basal, midzone and superficial layers; after menopause is atrophic with mainly basal and parabasal cells with high N/C ratio that resembles dysplasia; prepubertal girls have similar appearing epithelium
• Squamocolumnar (SC) junction: where squamous and columnar epithelium meets; lined by krt7+ non-stratified cuboidal cells; can migrate proximately as columnar epithelium is replaced by metaplastic squamous epithelium, due to increased estrogen production and growth of vaginal bacterial flora (new SC junction); recent studies support SC junction as site of “embryonic cell population”, involved in cervical remodeling (metaplasia and microglandular hyperplasia), and as cell of origin for cervical cancer and its precursors (J Pathol 2013;229:460)
• Transformation zone: also called ectropion, area between original SC junction and new SC junction due to regenerative metaplastic response; site of > 90% of squamous cell carcinomas and dysplasia
• Note: endocrine cells and melanocytes are seen occasionally in cervix; multinucleated giant cells may be a normal finding, often accompanied by edema (Arch Pathol Lab Med 1985;109:200)
• Basal cells (reserve cells): derived from SC junction cells (J Pathol 2013;229:460); cuboidal to low columnar with scant cytoplasm and round/oval nuclei; acquire eosinophilic cytoplasm as they mature; positive for low molecular weight keratin (krt5) and estrogen receptor; negative for high molecular weight keratin and involucrin
• Suprabasal cells: have variable amount of glycogen, detectable with Lugol/Schiller’s test (application of iodine) or microscopically by PAS stain; positive for high molecular weight keratin (p63) and involucrin
• Glandular epithelium: positive for estrogen receptor
• Menarche: ovaries produce estrogen, which stimulates glycogen update by cervical and vaginal mucosa, which promotes growth of endogenous vaginal microorganisms, which produce acid and drop in vaginal pH; basal/reserve cells respond by proliferating, causing squamous and columnar metaplasia; squamous epithelium overgrows columnar epithelium, obstructing crypt openings and forming Nabothian cysts; also produces acute and chronic inflammatory infiltrate

Drawings
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Location of glandular and squamous epithelium

Clinical images
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Squamocolumnar junction

Micro images
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Normal nonkeratinizing squamous epithelium

Various images of ectocervix (H&E, stains, EM)

   

Various images of transformation zone

Various images of endocervix (H&E, stains, EM)

Infoldings resemble glands

   

Endocervix

Endocervical canal (whole mount)

Normal exocervix

Squamocolumnar junction

Prepubertal squamous epithelium shows only
basal and parabasal cells with no maturation

Virtual slides
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Normal cervix

Cytology description
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• See cervix-cytology

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