Gynecologic Pathology

Procedure Description:

Pap Smears

The Pap smear is one of the most successful screening tests ever developed and has been credited with a 70% reduction in cervical cancer incidence. The American College of Obstetrics and Gynecology (ACOG) recommends women start getting Pap smears at 21 years of age. For women under 30, a screening interval of every 2 years is appropriate and after 30 a woman may go to a 3 year screening interval after having 3 successive negative smears assuming she does not have a history of moderate or severe dysplasia, has an intact immune system and is not HIV positive.

Although conventional Pap smears have been the mainstay for many years, currently most Pap smears are prepared as “thin layer” preparations in which the cells sampled from the cervix are put into a solution which is sent to the cytology laboratory where specialized equipment creates a thin layer of cells for the cytotechnologist and pathologist to review. Although more expensive than conventional smears, thin layer smears have been shown to consistently increase the detection of cervical cancer precursors (dysplasias, CIN, Squamous Intraepithelial Lesions) and are now the preferred method of Pap smear preparation. Spectrum Pathology has extensive experience in interpretation of both conventional and thin layer cytology preparations.

Abnormal Pap smears are interpreted using the Bethesda System, a standardized reporting system  recommended by the National Cancer Institute and recently updated in 2006. Using this system, approximately 3.0-3.5% of patients will have an abnormal Pap smear most of which will be minor abnormalities classified as “Atypical Squamous Cells of Undetermined Significance” (ASCUS). A smaller number will have low grade lesions and even fewer high grade lesions. The single most important aspect of Pap smear screening is to as cost effectively as possible detect and eradicate high grade squamous lesions since these are the precancers that, if left untreated, may progress to cervical cancer. The pathologist plays the critical role in classifying abnormal Pap smears according to the Bethesda system.

Virtually all cervical precancers and cancers are associated with infection by human papilloma virus (HPV). Since the vast majority of HPV is sexually transmitted, the epidemiology of cervical cancer is that of an infectious disease.  While many different HPV types exist, a subset of approximately 15-20 types cause the vast majority of genital tract disease. They can be divided into “high risk” and “low risk” types. Low risk viruses are seen only in low grade lesions and are not associated with cancers while high risk viruses are seen in both high grade and low grade precancers as well as invasive cancers. It is important to remember that the majority of HPV infections will be cleared by the patient and not cause cancer. Only after persistent (2-3 years) high risk viral infection does high grade precancer and ultimately cancer develop.

In addition to interpreting Pap smears, Spectrum Pathologists also interpret cervical biopsies taken at the time of colposcopy for abnormal Pap smears. The correlation of findings at colposcopy and the Pap smear is important in assuring maximal quality of care.

In the last 5-10 years the ability to use sensitive tests for the detection of HPV has been very helpful in managing patients with abnormal Pap smears. While there is no utility in testing for low risk viruses, the detection of high risk virus is helpful in managing women with ASCUS Pap smears. The problem with ASCUS Pap results is that a small percentage of women (about 5-8%) with this Pap smear diagnosis will be found to have high grade lesions in their cervix when they undergo colposcopy. Since all of these lesions will have HPV, the absence of high risk HPV types in women with ASCUS essentially eliminates the possibility that they are one of the 5-8% with high grade lesions, thus they can be safely followed up with only another Pap in one year. If a woman with ASCUS is positive for HPV it is recommended she undergo colposcopy to rule out a high grade precancer. In addition to using HPV testing to manage women with ASCUS, it is also used for primary screening in women over 30 years of age. In this setting, if a woman is negative for high risk HPV and has a normal Pap smear, she can be screened at a 3 year interval. Recently, an HPV vaccine has been developed and released for use in young women. It is important to remember that although effective, the vaccine does not cover all of the HPV types that cause cervical cancer and thus continuing to be screened with Pap smears is important.

Spectrum Pathology has extensive experience in interpreting Pap smears and cervical biopsy specimens and is unique in Maine and New Hampshire as having two pathologists, Dr. Michael Jones and Dr. Silvia Skripenova, with advanced subspecialty training in gynecologic pathology.  Dr. Jones has also participated in two Maine State cervical cancer task forces and has published widely in the area of cervical pathology.

Important Links:

www.asccp.org
www.acog.org
www.cancer.gov/cancertopics/factsheet/Detection/Pap-test
www.womeshealth.gov
www.cdc.gov/STD/HPV/