Lymphoma classification and the tools of our trade: an introduction to the 2012 USCAP Long Course.

The 2012 USCAP Long Course 'Malignant Lymphomas-Building on the Past, Moving to the Future' began with an introduction to lymphoma classification over the last half century and a discussion of our current diagnostic armamentarium, together with a look toward the future. The Rappaport classification, originally published in 1956, was a morphologic classification with few categories. The early 1970s saw a great and tumultuous revolution in the field with the publication of two functional lymphoma classifications that related the malignant lymphomas to the cells of the normal immune system-the Lukes/Collins classification from the United States and the Kiel classification from Professor Lennert and the European Lymphoma Club. With discord abounding, the NCI working formulation, published in 1982, satisfied some but was a step back to a morphologic-based classification. In 1994, the International Lymphoma Study Group published the REAL classification, which reflected state-of-the-art practice for that time, and was shortly followed by preparations for the modern World Health Organization (WHO) classification published in 2001 and revised in 2008. The WHO classification, created by hematopathologists working with the advice and consent of clinical hematologist/oncologists, recognizes numerous distinct entities, defined based on their histopathological, immunophenotypical, molecular/cytogenetic and clinical features. The classification requires use of a multiparameter approach to lymphoma diagnosis although we still rely heavily on histopathology. Immunophenotypical studies, whether using paraffin section immunohistochemistry and/or flow cytometry, are also critical in almost all circumstances. Molecular/cytogenetic techniques that are constantly changing have an increasingly important role, even if not always required. The full impact of next-generation sequencing is yet to be felt but we are beginning to catch a glimpse of what is in our future. Finally, one must not forget the great importance of clinical data in arriving at a diagnosis that best serves the patient, our ultimate goal.