Chronic lymphoproliferative disorders: classification and diagnosis.

The chronic lymphoproliferative disorders are morphologically, immunologically and clinically heterogeneous. Common features of these processes include T, B or natural killer cell immunophenotypes and terminal deoxy-nucleotidyl transferase negativity. The B cell lymphocytic disorders include B-chronic lymphocytic leukaemia, B cell prolymphocytic leukaemia, chronic lymphocytic leukaemia-prolymphocytic leukaemia, non-Hodgkin's lymphoma (including mantle cell lymphoma) in leukaemic phase, hairy cell leukaemia and splenic lymphoma with villous lymphocytes. The T cell chronic lymphoproliferative disorders include prolymphocytic leukaemia, adult T cell leukaemia-lymphoma, large granulated lymphocyte leukaemia and Sézary syndrome. Occasionally, a lymphocytic proliferation is encountered that does not satisfy the morphological or immunophenotypical criteria for any of the above categories. These processes are best left unclassified.