[Leptomeningeal tumor cell infiltrations as a first manifestation of an immunocytoma (Waldenstrom's macroglobulinemia)].

Immunocytoma (Waldenstrom's macroglobulinemia) is a rare chronic lymphoproliferative disorder of B-cell origin. It is characterized by the presence of large amounts of circulating monoclonal immunoglobulin M (IgM) and lymphoplasmocytoid bone marrow infiltration. Affection of the peripheral nervous system is common and causes polyneuropathy (5-10%). An isolated leptomeningeal infiltration by neoplastic cells is very rare and has been reported in few cases only. The diagnosis is difficult, in particular if cerebrospinal fluid (CSF) cytology is inconclusive. We present the case of a patient who developed a personality disorder and cognitive impairment. Initial CSF findings were compatible with chronic lymphocytic (aseptic) meningitis. The serologic detection of IgM paraproteinemia and bone marrow cytology suggested immunocytoma. The selective analysis of B-cell clonality in both whole CSF cell lysates and individual CSF cells using polymerase chain reaction (PCR) based amplification of the rearranged CDR3 region of the IgH gene revealed the presence of a monoclonal B-cell population and was diagnostic for leptomeningeal tumor cell infiltration by immunocytoma.