T-Cell/Histiocyte-Rich Large B cell Lymphoma

Question 1

What is the definition of THRLBCL?

Answer 1

• characterized by a limited number of scattered, large B cells
• background of abundant T cells and histiocytes

Note: can arise de Novo but new possibility of it arising within or from NLPHL

Question 2

What is the epidemiology of THRLBCL?

Answer 2

• mostly affects middle aged men
• accounts for <10% of all DLBCL

Question 3

What sites does TCHRLB usually involve ?

Answer 3

• affects lymph nodes
• but bone marrow, liver and spleen are often involved

Question 4

What are the clinical features of

TCHRLB ?

Answer 4

• Fever, malaise
• Splenomegaly and or hepatomegaly
• most cases at diagnosis are advanced stage
• the disease is often refractory to chemotherapeutic regimens in use
• Imaging:
  
  • NLPHL usuall affects one or two regions
  • TCHRLB usually is a systemic disease
    
    • usually a more PET avid disease

Question 5

What are the histological findings

of TCHRLB ?

Answer 5

• diffuse, vaguely nodular growth pattern
• most of the lymph node architecture is effaced
• scattered single large B cells are embedded in background small T lymphocytes
  
  • IMP: they do not form clusters or large aggregates
  • can be pleomorphic and resemble RS cells
• non-epithelioid histiocytes are often seen
• background lymphocytes are T cells
  
  • very few small B cells in background
• NO FDC meshwork is present

Question 6

What can be seen on recurrence of

TCHRLB ?

Answer 6

• morphology may look like DLBCL
• this portends a worse prognosis

Question 7

What types of lymphomas should not be

included in the category of TCHRLB ?

Answer 7

• B cell lymphomas with a spectrum of cell size and morphology and distribution
• clusters or sheets of large cells
  
  • these are better categorized as a subtype of DLBCL, NOS

Question 8

What is the immunophenotype of

TCHRLB ?

Answer 8

• Pan B cell markers are expressed:
  
  • CD19, CD20, and CD79a
  • BCL6 positive
• BCL2 and EMA
  
  • variable staining
• Negative
  
  • CD138, CD15 and CD30

Question 9

What is the immunophenotype of

background cells in TCHRLB ?

Answer 9

• variable CD68 and CD163 histiocytes
• CD3 and CD5 positive T cells
  
  • T cell rosettes around the tumor cells and remnants of B cell follicles or clusters of small B cells are absent in de novo TCHRLB
• lack of residual IgD+ mantle cells and lack of FDC meshworks helps differentiate from NLPHL