The document provides a detailed overview of the cervix's anatomy, emphasizing the ectocervix and endocervical canal, as well as key structures like the external os and transformation zone. It highlights the significant role of high-risk HPV infections in developing cervical cancer, accounting for a substantial number of cases and fatalities worldwide. Effective screening methods, particularly the Pap test, have been pivotal in detecting and treating cervical precursor lesions, ultimately improving prognosis for affected women.

1. Introduction

2. ANATOMY OF CERVIX :
•Ectocervix: External part, visible on vaginal exam, covered by mature squamous
epithelium.
•Endocervical Canal: Lined with columnar, mucus-secreting epithelium.
Key Structures:
•External Os: Small opening where squamous epithelium transitions into endocervical
canal.
•Squamocolumnar Junction: Meeting point of squamous and columnar epithelium,
position varies with age and hormonal changes.
•Transformation zone: The area of the cervix where the columnar epithelium coexists
with the squamous epithelium is termed the transformation zone.
Immature squamous cells in the transformation zone are most susceptible to HPV
infection, and as a result this is where the majority of cervical precursor lesions and
cervical cancers develop.

3. Cervical squamocolumnar junction showing a transition from mature, glycogenized
squamous epithelium to columnar endocervical glandular epithelium. The superficial,
mature squamous epithelial cells are not susceptible to human papillomavirus (HPV)
infection.The HPV- susceptible cells include immature basal squamous cells and
endocervical glandular cells.

4. Worldwide, cervical carcinoma is the fourth most common cancer in
women, with an estimated 570,000 new cases in 2018, of which more than
one-half will prove fatal.
No form of cancer better documents the remarkable benefits of effective
screening, early diagnosis, and curative therapy than does cancer of the cervix.
Most credit for these dramatic gains belongs to the effectiveness of the Pap
test in detecting cervical precursor lesions, some of which would have
progressed to cancer if not treated; in addition, the Pap test
can also detect low-stage, highly curable cancers.

5. PREMALIGNANT LESIONS OF THE CERVIX
High-risk HPVs are by far the most important factor in the development of cervical cancer.
HPVs are DNA viruses that are grouped into those of high and low oncogenic risk based on
their genotypes.
• High-risk (15 identified types); HPV-16 (60% of cases), HPV-18 (10% of cases).
• Low-Risk HPVs: Cause of sexually transmitted warts (condyloma acuminatum).
Genital HPV infections are extremely common; most of them are asymptomatic, do not
cause any tissue changes, and therefore are not detected on Pap test.
• Detection: Peaks in ages 20-24; many infections are transient.
• Clearing Rates: 50% cleared in 8 months, 90% in 2 years.
• Persistent Infections: Linked to cervical precursor lesions and cancer.

6. • Surfaces covered with mature, intact squamous epithelium, such as the
ectocervix, vagina, vulva, penis, and oropharynx, are normally resistant
to HPV infection.
• Sites in the female genital tract that are susceptible to infection include
areas of squamous epithelial trauma and repair, where the virus may
access basal cells, and the immature metaplastic squamous cells that are
present at the squamocolumnar junction of the cervix.
• The cervix, with its relatively large areas of immature squamous
metaplastic epithelium, is particularly vulnerable to HPV infection.
Other sites in the body: that are vulnerable to HPV infection include the
squamocolumnar junction of the anus and the squamous cells of
oropharyngeal tonsillar crypts.