ABSTRACT
I. INTRODUCTION Compelling evidence from histopathological, epidemiological, and molecular biological studies indicates that malignant transformation is the end result of an accumulation of alterations in the cellular genome (1). Most cancers are clonal, suggesting that a single cell that has acquired these changes is capable of giving rise to a malignant tumor. Although malignant cells from a number of tissues exhibit numerous mutations, recent work suggests that only a few critical alterations are required for malignant transformation (2).
