A 48 year old woman was admitted with a history of weakness for two months. On examination, cervical lymph nodes were found enlarged and spleen was palpable 2 cm ptatelet count 237 X 109L and total leukocyte count 40 x coarse clumped chromatin. Bone marrow revelaed a nodular lymphoid infiltrate. The peripheral blood lymphoid were negative for CD 19. CD5, CD 20 and CD 23 and were negative for CD 79 B and FMC - 7. What is the most likely diagnosis?