Surgery remains the mainstay of treatment for most classes of human so
lid tumours, with the principal exception of lymphomas, but it is insu
fficient in many cases to guarantee cure. With few exceptions, recurre
nt and metastatic solid tumours continue to defy attempts to develop e
ffective adjuvant therapies. Recent insights into tumour biology revea
l an increasingly complex picture of cell and molecular processes whic
h confer heterogeneity and resistance to treatment upon tumours. These
insights may also yield new targets for more effective adjuvant thera
pies.