This volume begins by reviewing selected malignancies in which the search for clinically relevant oncogenes has led to more focused studies on gain-of-function and loss-of-function genetic abnormalities, as well as autocrine and paracrine growth factor loops known to regulate tumour physiology and malignant cell behaviour. Many of these genetic and functional abnormalities are shared by several different tumour types and are not uniformly present in all tumours of the same type. This observation brings up molecular questions about the tissue-specific determinants that underlie individual cancers and also gives added impetus to the suggestion that molecular abnormalities (referred to as tumour markets) be included among the histopathologic features used for clinical diagnosis and management. The remainder of the volume updates molecular mechanisms relating to select growth factor systems, oncogenes, and tumour suppressor genes introduced earlier in the disease-oriented chapters.