Meningeal leukemia complicating prolymphocytoid transformation of B-chronic lymphocytic leukemia

A patient who developed a meningeal leukemia during prolymphocytoid transformation of B-chronic lymphocytic leukemia is described. The central nervous system (CNS) complication occurred after 5 years of relatively benign course. Almost all CNS mononuclear cells showed the typical morphology and immunology of prolymphocytic leukemia cells, whereas a mixture of prolymphocytoid elements and small-sized lymphoid cells was observed in peripheral blood. In this case the more aggressive component was present at diagnosis and showed an uncommonly slow progression allowing the occurrence of the CNS involvement.