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Microbiology

Cervical Cancer

This section focuses on the role of Human Papillomavirus (HPV) in cervical cancer screening, including the etiology, epidemiology, transmission, and disease states associated with HPV infections

Human Papillomavirus (HPV)

Etiology

  • Classification: A member of the Papillomaviridae family
  • Types: Over 200 types of HPV have been identified, with approximately 40 types infecting the genital area. These are broadly classified as:
    • High-Risk HPV Types: Associated with cervical cancer and other cancers (e.g., anal, oropharyngeal, vaginal, vulvar, penile). The most common high-risk types are HPV 16 and HPV 18, which account for approximately 70% of cervical cancers
    • Low-Risk HPV Types: Typically cause genital warts (condylomata acuminata) but are not associated with cancer. The most common low-risk types are HPV 6 and HPV 11

Epidemiology

  • Global Distribution: HPV is found worldwide
  • Prevalence: Extremely common, with most sexually active individuals acquiring an HPV infection at some point in their lives
  • Age Groups: Most infections occur in adolescents and young adults shortly after the onset of sexual activity

Transmission

  • Sexual Contact: Primarily transmitted through sexual contact, including vaginal, anal, and oral sex
  • Skin-to-Skin Contact: Can also be transmitted through non-penetrative skin-to-skin contact in the genital area
  • Mother to Child: Rarely transmitted from mother to child during childbirth

Disease States

  • Genital Warts (Condylomata Acuminata): Caused by low-risk HPV types (e.g., HPV 6 and HPV 11). These are benign growths on the genitals, anus, or surrounding skin
  • Cervical Dysplasia (Cervical Intraepithelial Neoplasia, CIN): Precancerous changes in the cells of the cervix caused by high-risk HPV types. Classified as:
    • CIN 1: Mild dysplasia, often resolves spontaneously
    • CIN 2: Moderate dysplasia, higher risk of progressing to cancer
    • CIN 3: Severe dysplasia, high risk of progressing to cancer
  • Cervical Cancer: Invasive cancer of the cervix caused by persistent infection with high-risk HPV types
    • Types: Most cervical cancers are squamous cell carcinomas, but adenocarcinoma is also common
  • Other Cancers: High-risk HPV types are also associated with anal cancer, oropharyngeal cancer (cancer of the throat and tonsils), vaginal cancer, vulvar cancer, and penile cancer

Cervical Cancer Screening

  • Purpose: To detect precancerous changes in the cervix before they progress to invasive cancer
  • Methods
    • Pap Test (Papanicolaou Test): Collects cells from the cervix to be examined under a microscope for abnormalities
    • HPV Test: Detects the presence of high-risk HPV types in cervical cells
  • Screening Guidelines: Vary by age and risk factors, but generally recommend:
    • Ages 21-29: Pap test every 3 years
    • Ages 30-65
      • Pap test every 3 years
      • HPV test every 5 years
      • Co-testing (Pap test and HPV test together) every 5 years
    • Over 65: Screening is typically not needed if previous screenings have been normal
  • Follow-up
    • Abnormal Pap Test: May require repeat testing, colposcopy (examination of the cervix with a magnifying instrument), or biopsy
    • Positive HPV Test: May require repeat testing, colposcopy, or genotyping to identify specific high-risk HPV types

Prevention

  • HPV Vaccine: Highly effective in preventing infection with high-risk HPV types. Recommended for:
    • Adolescents: Ideally administered before the onset of sexual activity (ages 11-12)
    • Young Adults: Can be administered up to age 26, and in some cases up to age 45
  • Safe Sex Practices: Using condoms can reduce the risk of HPV transmission, but they do not provide complete protection
  • Regular Screening: Following recommended cervical cancer screening guidelines can detect precancerous changes early

Important Notes

  • Persistent HPV Infection: Most HPV infections are cleared by the immune system within 1-2 years. Persistent infection with high-risk HPV types is the primary risk factor for cervical cancer
  • Risk Factors for Cervical Cancer: Persistent HPV infection, smoking, weakened immune system, multiple sexual partners, and long-term use of oral contraceptives
  • Early Detection is Key: Regular cervical cancer screening and HPV vaccination are essential for preventing cervical cancer

Key Terms

  • Etiology: The cause or origin of a disease or condition
  • Epidemiology: The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems
  • Transmission: The way a disease is spread from one person or source to another
  • High-Risk HPV Types: HPV types associated with cervical cancer and other cancers
  • Low-Risk HPV Types: HPV types that typically cause genital warts but are not associated with cancer
  • Genital Warts (Condylomata Acuminata): Benign growths on the genitals, anus, or surrounding skin
  • Cervical Dysplasia (Cervical Intraepithelial Neoplasia, CIN): Precancerous changes in the cells of the cervix
  • Cervical Cancer: Invasive cancer of the cervix
  • Pap Test (Papanicolaou Test): A screening test that collects cells from the cervix to be examined under a microscope for abnormalities
  • HPV Test: A screening test that detects the presence of high-risk HPV types in cervical cells
  • Colposcopy: Examination of the cervix with a magnifying instrument
  • Biopsy: Removal of a tissue sample for microscopic examination
  • HPV Vaccine: A vaccine that prevents infection with high-risk HPV types
  • Persistent Infection: An infection that does not clear on its own and continues to be present over time