Molecular Pathology of Cancer

Abstract

PCR has provided an opportunity to detect small quantities of cancer cells. This has been applied to the detection of micro- metastatic and microresidual cancers in the blood and bone marrow. Haematological cancers may present consistent abnor- malities of DNA with characteristic translocations which provide targets for detection. Successful detection of micrometastatic disease using these approaches is now common for several haema- tological cancers although the complexities of interpretation of the data must be emphasised. Technical problems are common and the extreme sensitivity of the technique may reveal translocations to be present at a low level in normal tissues. Solid tumours represent a greater technological challenge. Specific abnormalities of DNA are less well described. An alternative approach has been to detect the expression of genes which are specific to the tissue of origin of a cancer but are not normally expressed in the tissue under study for the presence of micrometastatic disease, usually blood or bone marrow. This approach has proved promising for a number of cancers, particularly melanoma, neuroblastoma, prostatic cancer, with some less certain success for breast and colorectal cancer. The clinical situations where useful information may be found include the detection of micrometastatic disease as part of staging, during and after treatment in follow-up and the detection of con- tamination of peripheral blood stem cell harvests. Data suggest that we should investigate the role of these techniques but the tech- nical challenges are considerable and comparisons between inter- ested laboratories have shown a persisting difficulty with false positive and negative tests.