During the last five years the histological classification of the non-Hodgkin lymphomas has become a complex subject. Even experienced pathologists and clinicians find it increasingly difficult to make their way through the extensive and often confusing literature. The confusion is mainly due to the fact that different "schools" use different starting points for their classifica tion. Moreover, since many immunological problems related to classifica tion have not been completely resolved yet, even researchers who use the same approach do not always arrive at the same classification scheme....