What is cervical dysplasia?

The term "plasia" means growth. Cervical dysplasia means disordered growth. It is easier to understand cervical dysplasia if we first examine the normal cervix. When we look at the lining of the normal cervix under a microscope we see layers of cells. The normal distribution is that the bottom layer is made of round young cells. As the cells mature they rise to the surface and flatten out, so that on the surface the cells are flat.

In cervical dysplasia there is a lack of this organized growth process. In mild dysplasia (CIN I) only a few cells are abnormal, while in moderate dysplasia (CIN II) the abnormal cells involve about one-half of the thickness of the surface lining of the cervix.

In severe dysplasia or carcinoma-in-situ  (CIN III) the entire thickness of cells is disordered, but the abnormal cells have not yet spread below the surface. Carcinoma-in-situ means "cancer in place". If this condition is not treated, it often will grow into an invasive cervical cancer.

In dysplasia and carcinoma-in-situ all of the abnormalities are confined to the surface lining (or "skin") of the cervix. In invasive cancer the cells are not only disordered throughout the entire thickness of the lining, but they invade the tissue underlying the surface. Invasive cancer is treated entirely differently than dysplasia.

Newer classification systems

It is important to realize that the different grades of cervical dysplasia are not a stepwise progression but rather represent a description ranging from a slight irregularity in the cells to a full thickness abnormality.  The most important concept is that dysplasia is limited to the "skin" of the cervix, and has not invaded into the underlying tissue.  Even "carcinoma-in-situ" is not invasive cancer.  In the past, there was a tendency to treat "carcinoma-in-situ" as a much more serious problem than severe dysplasia, when in fact they are essentially the same. 

Because of this confusion a new classification system for cervical dysplasia was developed.  Remember that "plasia" means "growth."   "Neoplasia" means "new growth."  The surface layer of cells ("skin") is called "epithelium."  Putting this together, a new growth within the epithelium is called "intraepithelial neoplasia."  If we are describing the cervix, then the term used is "cervical intraepithelial neoplasia," or "CIN." 

The grades of CIN are similar to the older system, with the difference being that severe dysplasia and carcinoma-in-situ both being placed in the category of CIN III.   Mild dysplasia is called CIN I and moderate dysplasia is called CIN II.

Again, you should remember that cervical dysplasia should be considered to be pre-cancerous, but not cancer.  Statistically, mild dysplasia is more likely to go away without any treatment that severe dysplasia, which has a higher probability of becoming invasive cancer over time if not treated.  To emphasize this, an even newer classification system was developed which simply calls dysplasia low grade (less likely to progress to cancer) or high grade (more likely to progress to cancer) if not treated.   Remember, it is extremely uncommon for dysplasia to progress to cancer if it properly treated and the women has regular follow up exams!

The Atypical Pap (ASCUS)

This is the category that drives women crazy!  This means some cells that are slightly funny looking, but not abnormal enough to call dysplasia.   (ASCUS stands for "atypical cells of undetermined significance.) This category could also be called "probably normal, but I want to keep a close eye on things."   There is a tremendous variation between labs on how many pap smears come back with this reading, which corresponds to the old "Class 2" classification.  Some labs will be very liberal in calling normal variations "atypical," which causes women to worry needlessly.  Other labs have stricter criteria for this classification.

Infection or vaginitis frequently causes this type of pap smear, so often the pap smear is repeated after the infection is treated.  It is common to get this type of pap smear after treatment of the cervix for dysplasia.  Since many studies show that 20% to 30% of women with this type of pap smear have dysplasia, it is a good idea to do colposcopy for pap smears that persist in showing these changes. 

Often these changes will persist off and on for years, but it is important to understand that this is not a significant problem if dysplasia has been ruled out be colposcopy.

How is Dysplasia Detected?

Usually the abnormal cells are first discovered on a routine Pap test. The pap test is a screening test that examines cells scraped off the surface of the cervix. When abnormal cells are seen on a Pap test, we must look at the cervix more closely to determine the exact nature of the abnormality. To do this we examine the cervix with a special microscope called a colposcope. This examination is called colposcopy.