All of the following are characteristic features of Diffuse Large B-Cell Lymphoma (DLBCL) EXCEPT:

Explanation

## Characteristic Features of DLBCL **Key Point:** DLBCL is the most common type of non-Hodgkin lymphoma (30–40% of all NHL). Understanding its defining features is essential for NEET PG. ### Immunophenotypic Profile | Feature | DLBCL | Comment | |---------|-------|----------| | CD20 | Positive | B-cell marker; target for rituximab | | CD79a | Positive | B-cell associated antigen | | CD5 | Negative | Helps exclude CLL/SLL | | CD23 | Usually negative | Helps exclude CLL/SLL | | Ki-67 | High (>40%) | High proliferation index | **High-Yield:** DLBCL is CD20^+^ CD79a^+^ CD5^−^ CD23^−^, which distinguishes it from CLL/SLL (which are CD5^+^ CD23^+^). ### Cytogenetic Abnormalities **Warning:** The t(8;14) translocation is characteristic of **Burkitt lymphoma**, NOT DLBCL. This translocation juxtaposes the MYC oncogene on chromosome 8 with the immunoglobulin heavy chain (IgH) locus on chromosome 14, leading to MYC overexpression. **Clinical Pearl:** While DLBCL may have complex karyotypes and occasional MYC rearrangements (in "double-hit" lymphomas), t(8;14) as a primary defining feature is specific to Burkitt lymphoma. ### Clinical Presentation & Course - **Aggressive behavior:** Rapid growth, B symptoms common - **De novo or secondary:** Can arise directly or transform from indolent lymphomas (e.g., follicular lymphoma → DLBCL) - **Age:** Median 64 years; can occur at any age - **Sites:** Nodal and extranodal involvement **Mnemonic:** DLBCL = **D**iffuse, **L**arge, **B**-cell (CD20^+^), **C**omplex karyotype, **L**arge cells. NOT t(8;14). ### Why t(8;14) is Wrong for DLBCL The t(8;14) translocation is the hallmark of **Burkitt lymphoma**, a separate entity characterized by: - Small to medium-sized cells (not large) - "Starry sky" appearance on histology - Extremely high proliferation rate (Ki-67 ~100%) - Endemic, sporadic, and immunodeficiency-associated forms While "double-hit" or "triple-hit" DLBCL may carry MYC + BCL2/BCL6 rearrangements, t(8;14) alone is not a defining feature of DLBCL. **High-Yield:** On NEET PG, if asked about t(8;14), think **Burkitt lymphoma** first. If asked about DLBCL cytogenetics, think **complex karyotype** or **BCL2/BCL6 translocations** in germinal center subtype. [cite:Robbins 10e Ch 13]