Cytological Diagnosis of Cancer: Its Uses and Limitations

Abstract

The results of our experience over 12 years, together with other published figures, are presented as a guide to the most important applications of cytodiagnosis. This type of examination is useful in two different ways: as a screening test for the detection of symptomless disease, particularly precancerous states ; and as a diagnostic aid when biopsy is inapplicable. As a screening test the cervical smear has been outstandingly successful and carcinoma-in-situ can now be found and treated in whole populations, so that cervical carcinoma has become a preventable disease. Cytological examination of the urine is of established value in industrial preventive medicine. Other applications to cancer detection are at present of dubious or minor importance. As a diagnostic procedure, cytological examination is applicable to sputum, washings from the gastro-intestinal tract, urine, serous fluids, cerebrospinal fluid, and various other materials. With experience a good standard of accuracy can be attained, but this varies with the type of material as well as with the observer. Avoidance of “ false-positive ” reports is of the greatest importance in diagnostic work, whereas in screening the emphasis is on sensitivity (avoidance of “ false negatives ”). In research applications a substantial false-positive rate disqualifies the whole of any series in which it occurs. It is very important to realize that no person, however expert in identifying malignant cells in any particular material, is in a position to pronounce about the cells in specimens with which he is unfamiliar. He must first study a series of relevant samples for which the answers are known, and refrain from making reports until he finds that his opinions are correct. The identification of tumour cells has to be learnt anew in each different context, and the errors of the observer and of the technique allowed for, before any results are acceptable. With this proviso, cytological examination can be considered a useful, and in some situations an indispensable, method of diagnosis of cancer ; moreover, it holds the unique promise, by population-screening, of eliminating at least one common type of malignant disease from the community. © 1965, British Medical Journal Publishing Group. All rights reserved.