Diffuse Large B Cell Lymphoma

Definition

Diffuse effacement of normal architecture
- Rare patterns
  - Sinusoidal
  - Rosettes
  - Myxoid stroma
Large non-cohesive cells make up over 50% of population or are present in confluent foci
- Usual appearance is large vesicular nuclei and prominent nucleoli
  - Rarely medium sized nuclei with same vesicular features
- Nuclei may be uniform or pleomorphic
  - May be mulitnucleated
Cytoplasm usually moderate to abundant
- May be clear to eosinophilic to basophilic
A small cell population may be present
- If over 50% small atypical B cells, consider diffuse mixed B cell lymphoma
- If over 90% small T cells or histiocytes, consider T cell/ histiocyte rich B cell lymphoma
- Small cells may occasionally be plasmacytoid
  - May be monotypic or polytypic
B cell phenotype required
40% present in extranodal sites
- Most frequently in GI tract
- May involve any site
Rare cytologic features
- Spindle cell morphology
- Signet ring cells
- Cytoplasmic granules
May arise secondary to other types of B cell lymphoma
- De novo
- Secondary to transformation of low grade B cell lymphoma
- In setting of immunodeficiency
Following variants are not considered distinct clinico-pathologic entities and are described on separate pages, still within the overall heading of diffuse large B cell lymphoma
Following are considered distinct entities and are described as separate diseases

Yasodha Natkunam MD PhD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: September 30, 2007