7.1 What makes cytology such an appealing diagnostic test for the clinician who suspects cancer in a patient?
Cytology is a quick, inexpensive and highly specific (i.e. false positives are rare) test for cancer in a symptomatic patient. Within a few hours of a specimen arriving in the cytology laboratory the clinician can be guided towards appropriate treatment or further tests.
7.2 Can you think of any cancers for which attempts have been made to employ cytology as a screening test, other than cervical neoplasia?
Bladder cancer and oesophageal cancer are two such examples. Unfortunately, cytology does not provide sufficient sensitivity for the detection of these cancers. For this reason early attempts to establish cytology as a screening modality for these diseases were abandoned.
7.3 Try to think of the detrimental effects of false positive and false negative cytology test results in both the screening and diagnostic scenarios. How do the two scenarios differ?
False positive results can cause unnecessary fear and anxiety in patients and can also make people wary of participating in screening programmes. False negative results can be very serious in screening programmes because undetected early disease can progress to cancer before individuals return for their next screen, and cancer is a disease that is often difficult and costly to treat. False negative results are usually less serious in the diagnostic situation, where patients with negative cytology will almost always be subjected to immediate further tests to diagnose the cause of their symptoms.
7.4 To what extent do morphological features reflect the biological behaviour of malignant cells? (Hint: think at the molecular level.)
The most obvious morphological changes seen in cancer cells are alterations in nuclear shape, size, and density. These changes are thought to be a direct result of genetic aberrations that are transcribed and translated into abnormal nuclear proteins. The nuclear membranes of cancer cells consequently lose the ability to maintain water balance between the nucleus and cytoplasm and this can result in nuclear swelling or shrinkage. The increased quantity of abnormal nuclear chromatin that often accompanies malignant transformation is responsible for the coarsened and hyperchromatic nuclei of cancer cells.
7.5 What is the most reliable feature that differentiates malignant from benign tumours?
Benign tumours are confined to a specific area and do not spread, unlike malignant tumours in which cells lose their cohesive properties and are capable of distant metastases.
7.6 Why are the morphological changes in epithelial cells of greater significance than the nonepithelial response to injury?
Injured epithelial cells undergo morphological changes that can sometimes mimic malignant transformation, thus giving rise to potential false positives. By comparison, non-epithelial cells rarely give rise to such difficulties.