Background
Morphological diagnosis of non-Hodgkin lymphoma (NHL) is usually based on lymph node biopsy. Bone marrow biopsy (BMB) is important for staging, and morphology alone can be challenging for subtyping. Immunohistochemistry (IHC) allows a more precise diagnosis and characterization of NHL using monoclonal antibodies. However, there is a need for a minimal panel that can provide maximum information at an affordable cost.
Methods
All newly diagnosed cases of B-cell NHL with bone marrow infiltration between 2017 and 2019 were included. BMB was the primary procedure for diagnosing B-cell NHL. Subtyping of lymphomas was performed by immunophenotyping using a panel of monoclonal antibodies on IHC. The primary diagnostic panel of antibodies for B-cell NHL included CD19, CD20, CD79, CD5, CD23, CD10, Kappa, and Lambda. The extended panel of antibodies for further subtyping included CD30, CD45, CD56, Cyclin D1, BCL2, and BCL6.
Results
All cases of B-cell NHL were classified into the chronic lymphocytic leukemia (CLL) and non-CLL groups based on morphology and primary IHC panel. In the CLL group, the most significant findings were CD5 expression, CD23 expression, dim CD79 expression, and weak surface immunoglobulin (Ig) positivity. In the non-CLL group, they were CD5 expression, positive or negative CD23 expression, strong CD79 expression, and strong surface Ig expression. An extended panel was used for further subtyping of non-CLL cases, which comprised CD10, Cyclin D1, BCL2, and BCL6.
Conclusion
We propose a two-tier approach for immunophenotypic analysis of newly diagnosed B-cell NHL cases with a minimum primary panel including CD5, CD23, CD79, Kappa, and Lambda for differentiation into CLL/non-CLL group and Kappa and Lambda for clonality assessment. An extended panel may be used wherever required for further subtyping of non-CLL.

Keywords: Non-Hodgkin lymphoma, Immunohistochemistry, Chronic lymphocytic leukemia, Non-chronic lymphocytic leukemia, Bone marrow biopsy