Diagnosis and Prevention of Cervical Cancer - Human Papillomavirus infection
Human Papillomavirus (HPV) is the main cause of most of the histological changes that affect the female reproductive tract that includes the vagina, cervix, external genitalia, and the anus.
HPV is considered the most common cause of the cervical CA that’s why we are going to talk about it.
Human Papillomavirus (HPV)
This is a DNA virus that infects the skin and the mucosal membranes. And there are more than 100 types of HPV and some of these viruses cause skin polyps and that why its named a papillomavirus , and its transmitted by skin to skin contact and there is around 30 types that is transmitted sexually. Genital HPV is very common and it infects around 75% of women in west countries through out there entire life.
General characteristics of Human Papillomavirus
- • It's part of papillomaviridae family that can be fully integrated with the DNA of the host cell. Humans are the only known source of this virus.
• There is more than 100 types of HPV that have different DNA sequences and there specific group called genital HPV that are dangerous especially HPV 16, 18, 31, 45, 58 in addition to HPV 33, 35,39, 51, 52, 56, 59, 68, 73, 82 that are known as an important factor for development of cervical cancer.
Signs and symptoms of infection with Human Papillomavirus:
- • Skin polyps:
- - Common warts
- Planter warts
- Flat warts, and this is found mainly on the arms, face, and forehead.
- Nail warts
• Anogenital warts (condylomata acuminata):
90% of cases are caused by HPV 6 and 11, and usually the infection with this virus is resolved spontaneously without appearance of warts or any other signs or symptoms and its worth mentioning that the virus types that cause the genital warts don’t cause cervical cancer.
• Respiratory papillomatosis:
HPV type 6 and 11 can cause a rare condition called recurrent respiratory papillomatosis in which the warts are formed in the larynx and other parts of the trachea and those warts can recur many times and it may need multiple surgeries and it can hinder the respiration and in extremely rare cases it might develop to cancer.
• Cancers that are related to HPV:
There are 6 types of HPV that are classified as dangerous viruses such as HPV 16, 18, 31, 45, because they have high ability to cause cervical, anal, vaginal cancer in addition to head, neck, and penile cancer. And they have a genetic relation such as E6 and E7 that are known as carcinogens that encourage the growth of the tumor and the malignant transformation.
Methods of spread of Human Papillomavirus and prevention:
Most of people can be infected with one of those cutaneous viruses during childhood period. The HPV has protein shell (strong, enable them to stay in the environment for long period of time), therefore avoidance of touching of metallic surfaces such as toilet floors may decrease the risk of cutaneous infections. The genital infection can spread quickly through the skin of the genitalia and the mucosal membranes and it can be asymptomatic. There are multiple strategies can be followed to decrease the risk of the diseases that can be developed from the genital HPV.
- • HPV Tests:
This test is done by detecting the genetic material (DNA) of the HPV. And like the Pap smear it's done on the cervical cells and it can be done at the same time as the Pap smear test. And it's done for the cases bellow:
- - Women who had atypical squamous cells that considered as abnormal cervical cells in the Pap smear to check for high-risk types of HPV. And if the test shows the presence of high risk types of HPV, then further approach like colposcopy or cervical biopsy should be considered.
- In the women older than 30 years as part of abnormal cervical cells screening.
Nucleic acid hybridization test is the most sensitive method for the detection of 18 types of HPV DNA in cervical samples. And it differentiate between tow HPV groups: the low risk group that includes types 6/11/42/43/44, and the high/intermediate-risk group that includes types 16/18/31/33/35/39/45/51/56/58/59/68, but it can't detect the specific type of HPV that present.
• HPV vaccine:
- - Two types of HPV vaccines are available, the Cervarix and the Gardasil, both protect against HPV-16 and HPV-18 that that cause 80% of anal cancers, 70% of cervical cancers, 60% of vaginal cancers and 40% of vulvar cancer. Gardasil also protects against HPV-6 and HPV-11 that cause 90% of genital warts.
- Both vaccines are given in 3 shots over 6 months.
- It's recommended for 11 and 12 years old girls and it can be given at age of 9 years, it can be given also for girls and women at age of 13 to 26 years who have not been vaccinated or completed the vaccine series yet. And it's not recommended for women at age of more than 26 years and the best way to screen for cervical CA at this age is by doing regular Pap tests.
- It should be given for females before they become sexually active and before they are exposed to HPV, it can be given for women who are sexually active but they may get less benefit because they may have already been exposed to some HPV types targeted by the vaccine.
- It's not recommended to be given during pregnancy, although studies found that it doesn’t harm the baby, but more researches is needed. Getting the vaccine during pregnancy is not an indication to end the pregnancy.
- The vaccine can't protect against all types of cervical cancer ( about 30% of cervical cancers will not be prevented by the vaccine) , therefore it's important to continue to be screened for cervical cancer ( Pap smear regularly) even after getting all 3 shots of the vaccine.
• Other ways to prevent HPV:
- - Use condoms with every time of having sex from start to finish, but HPV can infect areas that are not covered with condoms, so it not fully protect against HPV.
- To be in faithful relationship with one partner.
- Choosing a partner who had few or no prior sex partners.
- The only sure way of protection is to avoid all sexual activities.
• Avoid smoking as it increases the risk of cervical cancer.
The papanicolaou test (also called Pap smear) is a screening test that is used to detect the precancerous changes (cervical intraepithelial neuplasia CIN or cervical dysplasia) and the cancerous changes in the endocervical canal that are usually caused by sexually transmitted HPV, and it can also detect infections and abnormalities in the endocervix and the endometrium.
Normal PAP smear Abnormal PAP smear
Cervical intraepithelial neoplasia:
CIN is a premalignant transformation of cervical squamous cells and it's not a cancer, most of CIN cases remain stable or are cured by the immune system. Small percentage of cases might progress to cervical cancer if untreated.
Most common cause of CIN is human papillomavirus (HPV) especially the types 16 and 18. And its diagnosed by the Pap smear screening test, and if it was abnormal , then colposcopy of cervix is recommended.
Last Update: 2011-09-01