General Principles of B cell neoplasia

Question 1

B cell development and markers

Answer 1

Question 2

Neoplasms arising from precursor B cells

Answer 2

B-acute lymphoblastic lymphoma

Question 3

Pre-germinal center B cell neoplasms

Answer 3

Mantle cell lymphoma

Question 4

Germinal center B cell neoplasms

Answer 4

Follicular lymphoma
Burkitt’s lymphoma
DLBCL, GCB type
Hodgkin’s lymphoma

Question 5

Post-germinal center B cell neoplasms

Answer 5

Marginal zone lymphoma
Mucosal-associated lymphoid tissue lymphoma
CLL/SLL
DLBCL, Non-GCB type

Question 6

Answer 6

Centroblast

Larger GC cell with open chromatin, high N:C ratio.

Centroblasts reside in the dark zone of the GC.

They express low levels of surface immunoglobulins and switch off BCL-2, making them susceptible to apoptosis.

They are CD10 positive, BCL6 positive, LMO2 positive, HGAL positive, and BCL2 negative.

Question 7

Answer 7

Centrocyte

Smaller GC cells with angulated to twisted nuclei and a lower N:C ratio than centroblasts. Some just look like normal mature lymphocytes.

Reside in the light zone of the GC.

Express higher levels of surface immunoglobulins and have undergone somatic hypermutation and heavy chain class switching.

IRF4 (MUM1) downregulates BCL6 expression

BCL6 negative, IRF4/MUM1 positive.

Question 8

Answer 8

Follicular dendritic cell

Larger cell with relatively round nucleus and a prominent central nucleolus. The chromatin is slightly finer and paler than surrounding lymphocytes in a germinal center.

Unlike many other DCs, follicular DCs are of mesenchymal origin, not hematopoietic origin.

Stain for CD21/CD23.

Question 9

Answer 9

Marginal zone cells

Post-GC memory B cells.

Cytologically, MZ cells have small to medium size, pale-to-clear cytoplasm, irregular nuclei with dispersed chromatin, and inconspicuous nucleoli.

Reside in marginal zones of lymph nodes, spleen, and MALT. Marginal zones are often hard or impossible to see on H&E outside of the spleen.

Express pan-B antigens and surface IgM, sometimes low level IgD. CD5 and CD10 negative, BCL2 and HLA-DR positive.

Question 10

What are the cells in the area highlighted by the yellow arrows?

Answer 10

Mantle cells

Present in all secondary follicles, immediately surrounding the germinal center.

Mantle cells are pre-germinal center and are thus IgD or IgM positive.

Wild-type mantle cells are TCL1 positive.

Question 11

Plasma cell markers

Answer 11

CD138, BLIMP1, Cyclin D1

Loss of PAX5

Question 12

Pan-B cell markers

Answer 12

CD19, CD79a

PAX5 and CD20 (except plasma cells)