70 year old male presented with 3-months history of generalised weakness. On examination, bilateral axillary lymphadenopathy was noted. Histopathological examination of enlarged lymph node showed effacement of lymph node architecture by diffuse proliferation of small-sized, mature-appearing lymphoid cells. Peripheral blood showed lymphocytosis with presence of CD5-positive and CD23-positive B-cells. Which of the following is the most likely diagnosis of this patient?