RESUMEN
Positive and differential diagnosis of chronic lymphocytic leukemia [CLL] is based on immunophenotyping analysis. CLL is searched whenever a persistent lymphocytosis is found. To evaluate the performance of flow cytometry in etiologic diagnosis of lymphocytosis. Could it allow us to distinguish CLL from other causes of lymphocytosis? Blood samples from 104 adult patients having a rate of lymphocytes> 5000 ele/mm[3] persisting more than three months were analyzed using a large panel of monoclonal antibodies in three colors and Cell Quest software. Lymphoproliferative B disorder was retained in 83 cases, including 50 cases of typical CLL with Matutes score >/= 4 and 12 cases of atypical CLL with Matutes score = 3. Diagnosis of hairy cell leukemia and follicular lymphoma were guided by the respective specific antigen expression CD103 and CD10. Large granular T lymphoma [LGL-T] was the most common etiology of lymphoid T proliferation. Unusual cases of Natural Killer [NK] and NK/T proliferations were found. The Flow cytometry is a powerful tool to establish lymphocytosis etiological diagnosis; it avoids invasive investigations in a large number of cases