History of the Pap Smear
Dr. George Papanicolaou, 1883-1962
The Pap smear is called that because of the doctor who researched and published about the technique, thereby popularizing it. His research wad done with a pathologist named Dr. Herbert Traut, and it had a tremendous impact on reducing the number of deaths from uterine cancer, world-wide. At first it was hoped to catch cervical cancer in the early stages, but it has come to point out even pre-cancerous lesions that can be eliminated before sterilizing surgery would be necessary.
In this way, not only has this man prevented countless needless deaths, but also has made possible the existence of countless human beings who are the offspring of mothers who might have otherwise been sterilized by life-saving hysterectomies. He won many honors and, born in Greece, even became an American citizen.
But no Nobel Prize? What's the deal?
The colposcope is a stereoscopic microscope that can focus onto a cervix at the back of the vagina from a mount that sits at the end of the exam table. The examiner is still using his or her eyes, but of a greatly magnified cervix. This cannot give the detail that tissue under a slide can, but it is used to better identify lesions that can then be biopsied and then put on slides.
It was first introduced in Europe in the 1920s by Dr. Hans Hanselman. It took another 30-40 years for it to catch on in the USA, when it was popularized by Dr. Sheffey.
Techniques of Pap smear and colposcopy--the gory details
The inside of the uterus has glandular cells, and the outside of the uterus that pokes through the vagina (thereby making accessible a way out for a baby) is covered with vaginal-like cells. At some point just before the cervix ends to open into the vagina, the glandular cells are converted into the vaginal-like ones in a sort of "transformation" zone called the squamo-columnar junction (the squamous cells being the vaginal-like cells, the columnar cells being the glandular cells). In fact, most people in private practice call it the transformation zone, or TZ. Since this is the area where the columnar cells are being converted into the squamous cells, it's the area of hight metabolic activity--it's where the action is. Since cancers are wild and rapidly growing cells, it makes sense that they would pop up first wihere most of the action is taking place the fastest...the transformation zone. So getting a sample of the TZ would be the ideal retrieval of cells in a Pap smear. But a Pap is just a stick taking a swipe at the end of the cervix, so there is no way that this sloppy, loose scattering of cells on a slide can be identified as TZ cells. But if both columnar cells AND squamous cells are seen, then it can be assumed that the TZ has been adequately sampled.
That's the deal on a good Pap.
Sometimes previous treatment for cervical disease (like dysplasia) can cause a scarring effect that causes the TZ to recede up the canal, out of reach of the Pap stick--and even the brush that was introduced just for the purpose of increasing the yield from the TZ. In these cases, the Pap really isn't "complete," because it cannot be said that the TZ was adequately sampled. The American College of Obstetricians and Gynecologists says that this is O.K. if there's been adequate TZ sampling within the last two years.
There are other designations for the columnar vs. squamous cells. For instance, sometimes they're referred to as endocervical vs. ectocervical cells. Same thing, and an incomplete Pap (no columnar cells) may read, "Endocervical cells absent."
The Newer Pap Technologies
Improvements in Pap technique and interpretation have been made over the years. Today's modern Pap will not only screen for dysplasia and call yeast, bacterial vaginosis, and trichomonas infections as an additional feature, but will also identify the types of HPV so that a clinician can know whether the Pap is from a woman at high risk for the malignancy-causing types of HPV or not.
Since adequate sampling of the TZ is so important, adding the "cyto-"brush as a second part of the cell retrieval has improved on sampling. This brush is actually inserted into the cervical canal itself a bit, making more likely crossing the TZ.
ThinPrep, a proprietary sampling technique, uses two improvements--increased retrieval by splashing the sampling in a fluid container instead of smearing it on a slide where it can dry and be ruined, and using computer imaging software to inspect the sampling without the "pollution" of blood, mucus, or other interference. Some insurance companies won't pay for it, and a good question would be, "Why?"