Bulletin Spring‧Summer 1996

simiilarity breeds cusabiluity Applying Findings on Cervical Cancer to the Diagnosis ofNasopharyngeal Carcinoma Long Duration in the Progression of Cancer Cancer is adreaded disease, all the more so since we are frequently exposed to images of it in its later stages——afterit has destroyed tissues and organs, caused failure of function, and eventually death. While the precise events in the progression of cancer are not yet known, what we do know now is that there is a long interval between the first event that initiates cancer and its full clinical manifestation. The Process of Carcinogenesis Research done on animals in the course of this century and numerous clinical observations have contributed to our present understanding of carcinogenesis, i.e. the process of the genesis of cancer. For instance, repeated application of coal tar on rabbits' ears produced cancers of the skin. The procedure first induced papillomas (benign tumours), followed by carcinomas (malignant tumours). Further research revealed that there were changes in the cells of the skin long before the papillomas appeared, and there was another long interval before carcinomas were produced. Precancerous Changes While cancer statistics record deaths and diagnoses, they seldom record the incidence of those who harbour cancer cells which may develop into cancer. It is in fact possible now to detect precancerous changes in the respiratory tract, the urinary tract, the gastrointestinal system, the oral cavity, and the female genital tract, thanks to the hard work of generations of medical researchers. The Case of the Uterine Cervix Of the various sites mentioned, the best understood is that of the cancer of the uterine cervix. In the late nineteenth century, precise diagnosis of the cancer became possible with the introduction of histopathology, i.e., what a pathologist can see from a biopsy. However, a biopsy involves discomfort for the patient, for an operation has to be performed to take living cells from the uterine cervix for purposes of study and diagnosis. The next significant breakthrough came with the introduction of the Pap smear method which involves the use of exfoliative or abrasive cytological techniques. A smear of exfoliative cells (as opposed to living cells in a biopsy) from the uterine cervical lining is placed on a glass slide; the addition of some chemicals enables a study of the size, shape and colour of the cells, which can indicate whether the cells are cancerous. The method does away with the operative discomforts and the cost of taking biopsies while yielding the same accuracy. The changes as indicated by a Pap smear correlate well wit h what a pathologist can see from a biopsy of the cervix. This and the fact that it is a relatively easy test has resulted in its wide application for the screening and early diagnosis of cervical cancer, and has in many instances enabled a cure of the disease before it reaches the invasive stage. The Case of the Human Nasopharynx Histologically, the structure of the cells lining the human nasopharynx is curiously similar to that of the cervix. This prompted experts from the Precancerous Changes U t e r i ne C e r v i x 28