History of the "Pap" smear

When I was a pathology resident in 1982-1986, many pathologists used the classification developed by Papanicolaou consisting of grades 1-5. We were more sophisticated and used the system that included HPV changes, mild dysplasia, moderate dysplasia, severe dysplasia and carcinoma in situ. Of course this terminology was used in biopsy pathology and we tried to correlate them. We spent a lot of time quibbling about whether a particular case was HPV or mild dysplasia and whether another case was severe dysplasia or carcinoma in situ both on biopsies and cytology. At that time, we thought HPV changes were benign viral changes that would regress and dysplasia was the precursor lesion to cervical carcinoma. Eventually it was discovered that HPV was actually the cause of cervical dysplasia. So HPV changes and mild dysplasia were combined into one. A concept was published using the terminology of cervical intraepithelial neoplasia or CIN. It had three levels. CIN I was mild dysplasia including HPV changes; CINII was moderate dysplasia; CINIII included severe dysplasia and carcinoma in situ. So now, there was no more quibbling on the low or the high end of the spectrum. However, a problem still remained especially on cytology: how do we separate the middle grade lesions from the high and low grade ones? What difference did it make? There were several problems. First, pathologists all over the country used different classifications, some using class 1-5, some CIN and some descriptive. There was no uniformity in reporting. There was also lack of inter and intraobserver reproducibility, i.e. today I look at a smear and call it mild dysplasia. Next week I look at the same smear and call it moderate. The question arises as to whether these discrepancies make any difference for the treatment of the patient. At the National Cancer Institute in Bethesda, Maryland a group of experts got together to try and address these issues. In 1988, they published a system of reporting called The Bethesda System. They proposed a two tiered system: low grade squamous intraepithelial lesion (LSIL) and high grade squamous intraepithelial lesion (HSIL). LSIL included HPV changes and mild dysplasia (CINI). HSIL included moderate and severe dysplasia and carcinoma in situ (CINII and CINIII).