Submitting Author: Al-Quran, Samer Z., MD
Institution: University of Florida
Additional authors:Brian A Gray, Ying Lee
Session: T Lymphoblastic Leukemia/Lymphoma

An 8 year old male presented in February 2011 with fever, lymphadenopathy and leukocytosis. Peripheral blood sample was submitted for flow cytometric (FCM) analysis to evaluate for leukemia. A bone marrow biopsy was performed subsequently and submitted for FCM and cytogenetic analysis. Patient was treated with chemotherapy for leukemia. The patient had recurrence of disease with CNS involvement in August 2011, followed by remission. He subsequent received an allogeneic bone marrow transplant. A bone marrow biopsy was performed at day 100 after transplant (February 2012). The patient died shortly after in March 2012.

2/2011: The peripheral blood smear revealed markedly increased blasts (more than 90%) that are intermediate to large in size with high N:C ratio, relatively fine chromatin, slight nuclear membrane irregularities and prominent to inconspicuous nucleoli. They had agranular basophilic cytoplasm and no Auer rods were identified. The decalcified and formalin fixed bone marrow biopsy sample showed revealed markedly hypercellular marrow with extensive replacement by leukemic blasts. Rare atypical cells were identified in the CSF sample.

2/2012: The bone marrow aspirate and decalcified/formalin fixed bone marrow biopsy showed a cellular marrow with multilineage hematopoiesis and left shifted myeloid maturation. Bone marrow differential: 88% blasts,

5% granulocytes/myeloid cells,1% monocytes, 6% lymphocytes, 1% erythroid cells

2012 bone marrow aspirate:

Blasts: 2%

Promyelocytes: 10%

Myelocytes: 10%

Metamyelocytes: 7%

Neutrophils: 13%

Erythroid: 47%

Lymphocytes: 8%

Monocytes: 3%

2/2011: An abnormal population of T-lymphoid blasts was identified by FCM (92% of leukocytes) in the peripheral blood. The blasts expressed CD4, CD8, CD5, CD7, CD1a, PTK7 (dim), CD1a (dim), TdT and cytoplasmic CD3, without CD34, CD117, CD10, HLA-DR or any B-cell or myeloid-associated antigens. The blasts were also negative for MPO and NSE by cytochemistry. Limited FCM analysis of the bone marrow aspirate showed similar population of T-lymphoid blasts.

2/2012: FCM analysis showed a population of abnormal lymphoid T cells that are medium to large in size (4-6% of total cells). These abnormal cells were CD3+, PTK7-, CD4-, CD8+, CD7+, CD2+, CD5-, CD123-, alpha/beta+, gamma/delta-, CD34-, CKIT+. Assessment of T-cell clonality by FCM (TCR Vbeta analysis) showed that these PTK7+ cells have restriction of the VB13.1 subfamily (98%), consistent with a clonal population of T cells, representing lymphoid blasts.

2/2012: Immunohistochemistry showed scatted CD5(+) T cells.

Bone marrow 2011.

Abnormal karyotype was identified: 46,XY,t(7;9)(q?36;q34);t(8;14)(q24.2;q11.2)[11]/46,XY[9]

Interphase FISH studies:

BCR/ABL1 fusion - NEGATIVE

MLL rearrangement - NEGATIVE

ETV6 and RUNX1 fusion - NEGATIVE

D4Z1 locus copy number change - NEGATIVE

D10Z1 locus copy number change - NEGATIVE

D17Z1 locus copy number change - NEGATIVE

Bone marrow 2012. Abnormal karyotype was identified:

43~47,XY,+2,del(3)(p13p21),-4,del(5)(q11.2q13),del(6)(q?23.3),add(7)(p13),t(7;9)(q?36;q34),-8,t(8;14)(q24.2;q11.2),-10, add(10)(q22),add(11)(q23),del(11)(p11.2p12),add(16)(q11.2)[cp7]/46,XY[13]

Interphase FISH studies:

MYC gene locus rearrangement - POSITIVE. Involvement of the MYC gene locus was demonstrated in ~6% of cells examined.

1. PTK7, a recently described biomarker that is expressed in T-cell acute lymphoblastic leukemia (T-ALL), was helpful in this case to detect minimal disease at relapse. This was confirmed by cytogenetic analysis and FISH. PTK-7 is expressed by myeloid blasts and plasmacytoid dendritic cells but not by immature T-cells. Its expression by T cells in bone marrow samples is indicative of T-ALL.

2. In T-cell leukemia that show expression of TCR-alpa/beta, T cell clonality can be demonstrated by Vbeta analysis. Once a Vb-restricted T-cell population is identified, V-beta analysis allows for rapid and relatively simple monitoring of disease during and after therapy

3. Phenotype switch after therapy. The blasts at relapse lost expression of CD4, CD5 and CD8 with upregulated CD3. They retained expression of PTK7 with no expression of CKIT, CD34 or CD123. This was supported by the positive cytogenetic findings

4. Interesting cytogenetic features:

a. The leukemic blasts harbored the 8/14 translocation, with the deregulation of the MYC gene (8q24.21) via juxtapositioning to the TCRA/TCRD (14q11.2) gene loci. This trans-location is associated with T-cell ALL and is considered to reflect a poor prognostic finding.

MYC gene locus rearrangement was also detected by interphase FISH in the relapse specimens.

b. The 7/9 translocation, resulting in the formation of a hybrid gene fusion product involving the TCRB (7q34) and NOTCH1 (9q34.3) gene loci, is considered relatively rare but specific for T-cell ALL with a CD4+ and CD8+ phenotype.

T-cell acute lymphoblastic leukemia

T-acute lymphoblastic leukemia

Case 408