CD8 expression in a case of chronic lymphocytic leukemia with trisomy 12

Area of Science:

• Hematology
• Immunophenotyping
• Cancer Genetics

Background:

• B-cell chronic lymphocytic leukemia (B-CLL) is a common lymphoid malignancy.
• Typical B-CLL cells express B-cell markers and lack T-cell antigens.
• Aberrant antigen expression can occur in B-CLL, but T-cell marker expression is rare.

Observation:

• A case of B-CLL presented with unusual expression of the T-cell-associated antigen CD8.
• Two-color flow-cytometric analysis confirmed CD8 expression on neoplastic B-cells.
• Immunoglobulin heavy-chain gene rearrangement confirmed B-cell clonality, while T-cell receptor gene rearrangement was absent.

Findings:

• Ploidy analysis revealed a tetraploid cell population and a high S-phase fraction.
• Fluorescence in situ hybridization (FISH) detected trisomy 12 in the B-CLL cells.
• The aberrant CD8 expression in this B-CLL case suggests a potential distinct subtype.

Implications:

• This case highlights the phenotypic heterogeneity within B-CLL.
• Trisomy 12 and a high S-phase fraction may be associated with this CD8-expressing B-CLL subtype.
• Further studies on additional cases are crucial to establish the clinical and prognostic implications of CD8 expression in B-CLL.