This classification is based primarily on the presence of morpho logically identifiable cell types and growth patterns that can be correlated with the clinical behaviour of the tumour and, in some cases, with tumour markers in the serum. Although some of the histological terms and definitions have histogenetic impli cations, this classification is not meant to be histogenetic. The terminology adopted for individual tumours is based on their general acceptance and world-wide usage. Synonyms are includ ed only if they have been widely used in the literature or if they are considered helpful in...