CD5 Negative B-cell Chronic Lymphocytic Leukemia: Clinical and Biological Features of 42 cases

Abstract

Chronic lymphocytic leukemia cell (CLL) usually (95%) express B-phenotype and the CD5 antigen which is usually present on the surface of normal T cells. However, among B CLL, 7 to 20% do not express CD5. The significance of the lack of CD5 expression remains unclear. We reviewed 42 consecutive CD5⁻ B CLL seen in three French medical centers from 1985 to 1991 and compared them with 79 CD5⁺ B CLL. Immunophenotype studies were performed using indirect immunofluorescence under light microscopy as well as flow cytometry after 1988. B CLL was considered to be CD5 negative when less than 5% of mononuclear cells expressed CD5 after substraction of the number of T-cells. Cases with CD5⁻ B CLL had isolated splenomegaly more frequently (p = 2.10⁻⁷). They frequently expressed a higher level of surface immunoglobulin (S-Ig) or the switch mu/delta phenotype (p = 4.7 10⁻²). The median survival time was not reached but no significant difference between CDS negative and positive B CLL was observed at the time of our data analysis (p = 0.97). Clinical presentation of CD5⁻ B CLL seems to be different from other forms of B CLL. Although, no conclusion can be reached in terms of prognosis, CLL with low expression of CD5 should be regarded as a subtype of CLL with a different clinical presentation than CD5⁺ CLL.

Key Words:

• Chronic lymphocytic leukemia
• CD5 negative
• splenomegaly
• phenotype