CD5negative

CD5 is a cell-surface glycoprotein expressed on most T lymphocytes and on a subset of B cells. It participates in signal transduction and helps regulate lymphocyte activation and survival. CD5-negative status refers to cells that do not express CD5 on their surface, as determined by immunophenotyping methods such as flow cytometry.

In the context of B-cell neoplasms, CD5 expression is a key diagnostic discriminator. The most common CD5-positive B-cell disorders are chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and mantle cell lymphoma (MCL). By contrast, many other B-cell lymphomas are typically CD5-negative, including follicular lymphoma, marginal zone lymphoma, Burkitt lymphoma, lymphoplasmacytic lymphoma, and hairy cell leukemia. However, CD5 expression can be variable or absent in some cases, and aberrant expression may occur during disease progression or after treatment.

Assessing CD5 status is usually part of a broader immunophenotyping panel that also includes markers such as CD19, CD20, CD23, CD10, CD79a, and cyclin D1, along with light chain restriction and genetic studies when appropriate. The combined immunophenotype, morphology, and genetic findings guide differential diagnosis and subsequent clinical management.

Limitations include occasional atypical or transitional phenotypes, requiring integration with clinical context. CD5 negativity alone does not specify a single diagnosis but helps refine the differential among B-cell lymphoproliferative disorders.