High Grade B cell Lymphomas

Question 1

What are the IHC/flow cytometric findings of Burkitt lymphoma?

Answer 1

• moderate to bright CD20 and light chain express
  (+)
• CD10, BCL6, MYC, CD38 (bright), CD43, CD71 (usually strong, but may be partial), CD81 (bright), high Ki67

(-)
-BCL2

Question 2

What markers can be rarely positive in Burkitt lymphoma?

Answer 2

• CD5
• CD21 (variable, often seen in the endemic form)
• EBER-ISH, usually in endemic and immunocompromised forms

Question 3

What is the differential diagnosis of Burkitt lymphoma?

Answer 3

• DLBCL
• HGBL with double or triple rearrangements
• HGBL, NOS
• Burkitt lymphoma with 11q aberration
• Plasmablastic lymphoma
• Florid follicular hyperplasia (biopsy sp)
• Mantle cell lymphoma, blastoid variant
• B-ALL
• T-ALL
• AML, myeloid sarcoma
• Non-heme small round blue cell tumors

Question 4

In working up a high grade B cell lymphoma, which IHC should be used?

Answer 4

• CD3, CD20, Pax5
• CD10, BCL6, MUM1
• BCL2, MYC, CD43
• EBER-ISH, CD30, Ki-67
• Cyclin D1, CD5, TdT

Question 5

What is a key immunophenotypic difference between BL and DLBCL?

Answer 5

• DLBCL does not typically express CD10 and CD43 without expression of BCL2

BUT rare cases can have a similar BL IHC pattern: (+) CD10, CD43, BCL6 and (-) for BCL2. Differentiation by proliferation index <90% would be key

Question 6

How can a HGBL, NOS be differentiated from Burkitt lymphoma?

Answer 6

• may morphologically appear the same
• NO MYC translocation present

Question 7

How can HGBL with double or triple hit be differentiated from Burkitt lymphoma?

Answer 7

• the presence of rearrangements of BCL2 and/or BCL6 in addition to MYC
• may also have strong expression of BCL2

Note: BL will only have MYC rearrangement

Question 8

How can plasmablastic lymphoma be differentiated from Burkitt lymphoma?

Answer 8

• PBL will be negative for CD45 (minor subset of cases may be CD45 dim)
• No expression of B cell markers is seen
• plasma cell markers (MUM1, CD38, and CD138) are positive and often CD56

Note: Ki67 will be high in both entities

Question 9

How can blastoid mantle cell be tricky by immunophenotype?

Answer 9

• A subset may be CD10+ and display morphology similar to Burkitt lymphoma (blastoid type)
• would lack the MYC translocation and have the cyclin D1
• would be positive for CD5 and have a lower proliferation index

Question 10

How can B-ALL and T-ALL be differentiated from Burkitt lymphoma?

Answer 10

• B-ALL and T-ALL will be (+) for CD34 and TdT
• they should lack BCL6 expression (most cases) and lack surface immunoglobulins

Question 11

What markers should T-ALL express?

Answer 11

• CD3 (with additional T cell antigens)
• TdT, CD34
• CD1a

Question 12

If there is a concurrent MYC and CCND1 rearrangement how should the lymphoma be classified?

Answer 12

• if blastoid morphology this would be a blastoid Mantle Cell Lymphoma
• given that CCND1 is a founder mutation

Question 13

What is the differential diagnosis of a HGBL with double or triple hit?

Answer 13

• DLBCL
• BL
• Double hit follicular lymphoma (MYC and BCL2 rearrangement)
• transformation of a lower grade lymphoma to higher grade
• B-ALL
• T-ALL
• AML, myeloid sarcoma
• HGBL, NOS
• HGBL with double or triple hit and TdT expression
• Non-heme small round blue cell tumors

Question 14

When FL has lymphoblastic transformation what immunophenotype would you expect?

Answer 14

• expression of TdT, loss of BCL6 and variable loss of immunoglobulin chains
• persistence of Pax-5, BCL2 and CD10