Classifications of lymphoma; reflections of time and technology.

'Nowhere in pathology has a chaos of names so clouded clear concepts as in the subject lymphoid tumors'. R.A. Willis. In 1858, Rudolf Virchow, with a primitive microscope and limited experiential base, recognized 'at least three different conditions here, hyperinosis, leucocytosis and leukemia….'. One hundred and fifty years later, the World Health Organization (WHO 2008), with a much more extensive armamentarium of tools, and a wealth of diverse experience, promulgated criteria distinguishing more than 100 types of 'Tumors of the Hematopoietic and Lymphoid Tissues'. From three to one hundred and three; this is progress! And this is history! Our goal is to examine the course and causes of this history; how we moved from three entities to a hundred and three, what we have learned from it, and how we may use the insights that we have gained to anticipate 'future histories' in this marvelously dynamic area of biology and disease.