Human papilloma virus

Definition

Human papilloma viruses (HPV) are a large group or related viruses, some of which play a part in the development of cervical epithelial cancers. HPV is also associated with skin cancer, oral and anal cancers.

Description

The family of human papilloma viruses includes a large number of genetically related viruses. Many of these cause warts, including the warts commonly found on the skin. Another group of HPV preferentially infect the mucosal surfaces of the genitals, including the penis, vagina, vulva, and cervix. These are spread sexually in adults. One group of HPV that infect the genitals causes soft warts, often designated condyloma acuminata. These genital warts are quite common and rarely, if ever, become cancerous. The most common of these low-risk HPV types are designated HPV 6 and 11. The second group of viruses, termed high-risk HPV types, is associated with the development of cervical cancer . Individuals infected with these viruses are at higher risk for the development of precancerous lesions. Typically, infection with these viruses is common in adolescents and women in their twenties, and usually do not result in cancerous growth. The most common high-risk HPV is type 16. The appearance of abnormal cells containing high-risk HPV types is seen most frequently in women over the age of 30 who have abnormal Pap smears.

HPV infections are very common. At some point in their lives, greater than 75% of people are infected with HPV, making HPV the most common sexually transmitted disease. In general, HPV infections do not cause any obvious symptoms increasing the likelihood of sexual transmission. Genital warts will occur in 1 or 2 of every 100 people. Abnormal Pap smears with atypical cells due to HPV can occur in 2-5% of women. If untreated, these women are at increased risk to develop cervical cancer. Virtually all cases of cervical cancer involve high-risk HPV types. It is believed that most cervical cancers take about five years to progress from early cellular changes to an invasive, life-threatening cervical cancer. It is not fully understood why most infections with high-risk HPV are of short duration, while a small percentage persist and eventually transform cervical cells to a state of cancerous growth.

The relationship among HPV, precancerous cellular changes, and cervical cancer have led to the suggestion that testing for the presence of HPV can be a useful addition to Pap smears. Pap smears involve microscopic analysis of cells removed from the cervix. The results of these tests are generally reported as normal, or consistent with the presence of cancer or a precancerous condition. Patients receiving the latter diagnosis usually are treated, either by excisional or ablative therapy surgery or some other means, in order to remove the tumor or precancerous lesion. In some cases the cytologist or pathologist examining a Pap smear reports a "borderline" result when abnormal cells are observed; but it is not possible to distinguish whether the changes seen are due to early precancerous changes, or inflammation caused by some infectious agent or irritant. In these cases, some physicians and scientists believe that testing for the presence of HPV can help to identify those women who should be closely followed for the development of early cancerous lesions, or who should undergo colposcopy, a procedure to examine the cervix for precancerous lesions. These cancer precursors, termed cervical intraepithelial neoplasia (CIN) when identified early, before they have become invasive, can almost always be completely removed by minor surgery, essentially curing the patient before the cancer has had a chance to develop. The cervical tissue removed, which includes the precancerous tissue, is examined as part of a biopsy to confirm the diagnosis, and if requested by a doctor, can be tested for the presence of high-risk HPV types. This does not occur often.

Treatments

In 2001 the only accepted treatment for HPV-related lesions is removal or eradication. Since the incidence of latent and recurrent infections is high, the eradication of HPV is not always 100% effective. It is essential to be aware that HPV is a sexually transmitted disease and women must engage in safe sex practices to decrease the risk of spreading the virus or becoming re-infected. The development of an HPV vaccine that would render individuals resistant to infection by at least some of the high-risk HPV types is a matter of considerable interest. It is possible that by 2010 such a vaccine will be available.

Resources

PERIODICALS

Cuzick J. "Human papillomavirus testing for primary cervical cancer screening." JAMA 283 (January 2000):108-9

Cox J.T. "Evaluating the role of HPV testing for women with equivocal Papanicolaou test findings." JAMA 281 (May 1999):1645-7.

ORGANIZATIONS

National HPV and Cervical Cancer Prevention Resource Center. <http:www.ashastd.org> June 2001.

Herpes.Org. <http:www.herpes.org> June 2001.

OTHER

"HPV -The culprit behind cervical cancer." Mayo Health <http://www.mayohealth.org/home?id=HQ00889> 29 June 2001.

Antopia's HPV Page. <http:www.antopia.com/hpv> 29 June 2001.

Warren Maltzman, Ph.D.

KEY TERMS

Ablative

—Also known as "Ablation" and referring to the surgical removal of lesions associated with HPV.

Biopsy

—The removal of a small bit of tissue for diagnostic examination

Cervical intra-epithelial neoplasia (CIN)

—A pre-cancerous condition in which a group of cells grow abnormally on the cervix but do not extend into the deeper layers of this tissue.

Colposcopy

—Procedure in which the cervix is examined using a special microscope.

Epithelial

—Referring to the epithelium, the layer of cells forming the epidermis of the skin and the surface layer of mucous membranes.

High-risk HPV type

—A member of the HPV family of viruses that is associated with the development of cervical cancer and precancerous growths.

Pap smear

—A test that checks for abnormal cells that can lead to cervical cancer.

QUESTIONS TO ASK THE DOCTOR

• If my Pap smear is abnormal, do you think I should have an HPV test?
• Based upon my Pap smear result and HPV testing, when should I have my next Pap smear?
• What can I do to decrease my risk of becoming (re)infected with HPV?