Histopathology, Morphology and Immunophenotyping of CLL

Abstract

Chronic lymphocytic leukaemia (CLL) is a low grade lymphoproliferative disorder (LPD) characterized by accumulation of monomorphic small mature lymphocytes in peripheral blood, bone marrow and lymphoid tissues. CLL was recognized as a separate clinical disorder towards the beginning of the twentieth century only, although leukaemia was first described in 1845. Even though in the early part of the century there were several case summaries and some mention about CLL in the text book published by Sir William Osler, The Principles and Practice of Medicine, the first comprehensive clinical reports on 80 patients with CLL were published by Minot and Isaacs in 1924 [1–3]. As with any other types of leukaemia, the diagnosis was initially purely based on morphology and over many years several diagnostic tests were introduced which helped to distinguish the various low grade LPDs with somewhat similar morphological appearance, which were originally all considered to be CLL. Currently the diagnosis of CLL can be made in a majority of patients by morphology and immunophenotyping of peripheral blood, but a minority of patients need an integrated approach including tissue histology and the analysis of chromosome deletions, duplications and translocations to make an accurate diagnosis. The distinction of CLL from other similar LPDs is important prognostically as well as increasingly in targeting specific therapies.