Immunohistochemical algorithms and gene expression profiling in primary cutaneous B-cell lymphoma

Area of Science:

• Hematology
• Oncology
• Pathology

Background:

• Classifying the cell of origin (COO) in Diffuse Large B-cell Lymphoma (DLBCL) is crucial for prognosis and treatment.
• Nodal DLBCL (nDLBCL) is typically categorized into Germinal Center B-cell (GCB) and non-GCB subtypes using immunohistochemistry (IHC).
• The applicability of these IHC algorithms to Primary Cutaneous B-cell Lymphoma (PCBCL) remains less defined.

Purpose of the Study:

• To evaluate if established IHC algorithms for nDLBCL can be applied to classify PCBCL subtypes.
• To determine which IHC algorithm performs best for classifying PCBCL.
• To compare IHC-based classification with gene expression profiling (GEP) in PCBCL.

Main Methods:

• A retrospective case-control study involving 14 PCBCL and 14 nDLBCL cases.
• IHC analysis of CD10, BCL6, MUM1/IRF4, BCL2, MYC, and Ki-67 expression.
• Classification using three distinct IHC algorithms and comparison with Lymph2Cx GEP results.

Main Results:

• All IHC algorithms classified cases into GCB and non-GCB subtypes.
• GEP identified 12 GCB, 12 activated B-cell-type, and 4 unclassified PCBCL cases.
• IHC classifications demonstrated concordance with GEP findings.

Conclusions:

• IHC algorithms are applicable for classifying PCBCL into GCB and non-GCB subtypes, similar to nDLBCL.
• The evaluated IHC algorithms are concordant with GEP, providing reliable classification for PCBCL.
• These findings support the use of IHC for subtyping PCBCL, aiding in diagnosis and potentially guiding treatment strategies.