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This article reports the historic background leading to the introduction of cervical smears as a tool in the detection of precancerous changes in the uterine cervix. The false-negative error rate in the primary screening process is discussed and illustrated by data recently compiled from this laboratory. Rescreening of approximately 25% of cervical smears yielded an error screening rate of approximately 5% of precancerous lesions and cancer of the uterine cervix. The total false-negative screening error rate was much higher but was unknown and should be determined by additional studies. The reasons for the false-negative screening errors are discussed. Some of the proposed remedies, particularly screening of the entire population for human papillomavirus infection, are judged to be unacceptable because of the high prevalence of this virus in well women and because the biologic events linking the presence of viral DNA with the development of precancerous lesions are unknown. Screening assistance with the help of a newly developed interactive machine, combining image analysis with a neural net was promising as a tool in quality control. Cancer 1993; 71:1406-12.

Flow cytometry provides a method for measuring the level of any substance within a cell for which a fluorescent marker is available. As such instruments have become more widespread, researchers have used them to measure the DNA content of cells from human cancers in the hope that this information may be of prognostic value. Indeed, many studies have demonstrated an association between abnormal DNA measurements and greater likelihood of adverse outcome. However, this is not true for all forms of cancer. As with any new technique, there may be technical problems with the method itself, which must be considered when interpreting results or devising ways to improve the technique's effectiveness. Researchers investigating the potential use of flow cytometry of DNA in the prognosis of colon cancer have identified a source of sampling error which may hamper the interpretation of results. Generally, flow cytometry is performed on small cancer specimens that can be spared by the pathology lab or on archival material. In the present study, investigators examined separately three samples each of 60 different colon cancers. In 38 cases, the DNA measurements on all three samples gave the same indication. In the remaining cases, one of the three samples yielded measurements different from the other two. In general, a DNA content that is indicative of an aneuploid chromosome complement, that is, having an abnormal number of chromosomes within the cell, is associated with an adverse outcome and is therefore the observation of interest. The results of the present study indicate that many tumors are diverse, and that the measurement of a normal diploid DNA content on any single sample may risk failing to identify aneuploid regions elsewhere in the tumor and misclassifying the chromosome complement as normal. (Consumer Summary produced by Reliance Medical Information, Inc.)