Lymphocytosis and chronic lymphocytic leukaemia: investigation and management.

Lymphocytosis is a common blood-test finding. Establishing whether the cause of lymphocytosis is benign or malignant is key to managing patients appropriately. A lymphocytosis should always prompt clinical review including a thorough history, examination and appropriate preliminary investigations (blood tests, blood film). The majority of patients with chronic lymphocytic leukaemia (CLL) present incidentally due to a lymphocytosis found on routine blood tests. Patient outcomes vary considerably based on genetic pre-disposition and various prognostic markers (age, Binet or Rai staging, and B2-microglobulin). Although not curative, chemo-immunotherapy is an effective treatment strategy for the majority of CLL patients with progressive disease. More recently, novel oral therapies have been developed that target key signalling and apoptosis pathways and that are being used in relapse settings and as first-line treatments for certain patients. © Royal College of Physicians 2022. All rights reserved.