CP Unknown

Heme-10/19/2011Kumaran Mudaliar and Girish VenkataramanLoyola University Medical Center, Pathology

What cells are the purple population?-Plasma cells

What cells are these?- hematogones

Additional plot of same case

Explain the gates in this tube containing CD45, CD19, CD20, kappa and lambda

Primary gate CD19/SSCLight chain negative cells colored greenand forwarded to show on all plots.

Hematogones• Hematogones: physiologic precursors of B-cells • 70 years ago, distinct ‘lymphoid appearing cells’ in the bone

marrow (BM). • ‘Hematogones’ (hematogonia, meaning ‘blood-maker’)• 662 patients– 8% pts had 5% or more of hematogones• 24.6% < 16 YO had hematogones• 6.3% > 16 YO had hematogones

• MC in patients: lymphoma, marrow regenerative states, immuno cytopenias, AIDS

Problem

• At 5% level, they are conspicuous on marrow smear and can be confused with neoplastic lymphoblasts

Reference Ranges?

• No accepted reference ranges – BM examination is not performed in healthy people

3 stages of Hematogone Maturation

• Early– Usually comprise a small

minority, but can become expanded in regenerating marrows

– No expression of CD 20 /CD34+

• Intermediate – Majority in most marrows – -CD34-/CD20 dim/CD10+

• Late– In contrast to mature B cells,

Cd34-/CD20+/maintain dim CD10 . Light chain surface+

Gated on all CD19+ cells

Stage 1HematogonesCD34+/CD10+

Stage 2 hematogonesDimmer CD10, CD20 het

Stage 3 hematogones-bright CD20, dim CD10

>90% of B-cells in this case are hematogones

Stg 2 (red) and stg 3 (blue)Hematogones lack CD34

Immunophenotype

• CD 10+ • CD 19+ • CD 20+ Variable expression• CD 38+ • CD 45+• TdT + [subset]• CD 34 + [subset]• Kappa & Lambda -

Differences between hematogones and lymphoblasts

• Both present in CD 45 dim gate • Hematogones: low side scatter – Consistent, highly reproducible, maturational pattern – No aberrant or asynchronous antigen expression

• B-ALL: relatively higher side scatter – Phenotypic abnormalities:

• Myeloid Markers: 13, 33, 15• T-cell: 2, 5, 7• Concurrent expression: TdT and cytoplasmic IgM; 34 and

20 ; 34 and surface light chains • Loss of antigen expression on blasts: 45 – ; 10 – [B-ALL with

MLL abnlties] ; 34 – [E2A-PBX1 fusion]

• Even tho both may express an antigen, difference in expression patterns and levels of specific antigens exist – IF TdT: hematogones (coarsely granular / speckled)

to blasts (finely granular / even distribution)– Also, hematogones have higher #’s of TdT and CD

10 molecules / cell • Leads to brighter expression on FC

– Hematogones have less CD 19 molecules/ cell• Hence dimmer expression on FC

BM Core Biopsies

• Hematogones: dispersed throughout marrow• Blasts: small clusters (> 5 cells)

Issues

• Differentiation can be challenging• Left Shifted Hematogones– Early stages after BM transplantation

• Anti-CD20 immunotherapy– Majority of B-ALL lack CD20 expression .

• -Phenotypic change

Sources

• McKenna RW, et al. Immunophenotypic analysis of hematogones (B-lymphocyte precursors) in 662 consecutive bone marrow specimens by 4-color flow cytometry. Blood. 2001 Oct 15;98(8):2498-507