<unk>  <unk>  is an asymptomatic condition in which individuals have increased blood levels of particular subtypes of<unk>  lymphocytes (i.e. an aberrant and potentially malignant group of lymphocytes produced by a single ancestral<unk> . This increase must persist for at least 3 months. The lymphocyte subtypes are B-cells that share certain features with the abnormal clones of lymphocytes that circulate in chronic lymphocytic leukemia/small lymphocyte lymphoma (CLL/SLL) or, less frequently, other types of B-cell malignancies. Some individuals with these circulating B-cells develop CLL/SLL or the lymphoma types indicated by their circulating<unk>  B-cells. Hence,<unk>  is a premalignant disorder In 2017, the World Health Organization (WHO) reclassified<unk>  as a distinct entity in which individuals have: 1) an excessive number of circulating<unk>  B-cells; 2) lack evidence of lymphadenopathy, organomegaly, or other tissue involvements caused by these<unk> s; 3) no features of any other B<unk>  lymphoproliferative disease such as one of the B-cell lymphomas; and 4) evidence that these<unk> s have either a CLL/SLL, atypical CLL/SLL, or non-CLL/SLL phenotype based on these<unk> s' expression of certain marker proteins. A fourth<unk>  phenotype,<unk> -marginal zone (i.e.<unk> -MZ) appears to be emerging as a distinct form of non-CLL/SLL<unk> .<unk>  consist of two groups: low-count<unk>  has blood B-cell counts 9<unk> s/liter (i.e. 0.5x9/L) whereas high-count<unk>  has blood B-cell counts ≥0.5x9/L but 9/L. While low-count<unk>  does not progress to a malignant disease, high-count<unk>  does so at a rate of 1-2% per year. MLP-MZ is an exception to this rule in that it s usually associated with B-cell counts >3x109/L and all cases, regardless of B<unk>  counts, have a somewhat higher risk of progressing to a malignant stage. The incidence of all<unk>  phenotypes increases with age and is strikingly high in the elderly. Below age 40,<unk> 's incidence is 90 may be as high as 75%. Age along with B-cell blood counts,<unk>  phenotype, and certain genomic abnormalities in the<unk>  B<unk> s are critical considerations in evaluating the clinical implications of<unk>  and its need for management.
Monoclonal B-cell lymphocytosis
Persistent polyclonal B-cell lymphocytosis
Abscess of thymus
Idiopathic CD4+ lymphocytopenia
Cutaneous lymphoid hyperplasia
Persistent generalized lymphadenopathy
Thymic hypoplasia
Lymphoid neoplasms with plasmablastic differentiation