Institution: Columbia University Medical Center, New York, NY
Additional authors:Bachir Alobeid,MD, Govind Bhagat,MD, Daniela Hoehn, MD,PhD
Session: B Lymphoblastic Leukemia/Lymphoma
HISTORY
One-year old male who presented with difficulty walking for 1 month and was found to have patchy marrow enhancement on MRI suspicious for an infiltrative process. On admission, his complete blood count was the following: WBC 7.4x10^9/uL, hemoglobin 9.9 g/dL, platelet count 319x 10^9/L. The first and second iliac crest bone marrow biopsy samples, with concurrent flow cytometric analyses, detected hematogones and an atypical population within the CD45 dim gate. Flow cytometric analysis of the peripheral blood sample collected at the same time detected no abnormal population. The patient developed diffuse lytic lesions and hypercalcemia over the course of several weeks. A targeted bone marrow biopsy (of a lytic bone lesion) was performed, which was diagnostic of B-cell acute lymphoblastic leukemia (B-ALL). He underwent chemotherapy and was in remission on evaluation 4 months later.
DETAILS
The first and second bone marrow biopsies were fixed in Bouin’s solution, while the diagnostic biopsy was fixed in formalin. The bone marrow aspirate smears were stained with Wright-Giemsa. Unfixed aspirate samples were submitted for flow cytometric, cytogenetic and molecular analyses.
IMMUNOHISTOCHEMISTRY AND FLOW CYTOMETRY
Histologic examination of the first and second bone marrow biopsies, and concurrent aspirate smears, showed normocellular marrow with diffuse infiltration by lymphoid cells ranging from mature appearing small lymphocytes to medium sized cells with dispersed chromatin, which was compatible with hematogones. The background cellular elements consisted of maturing trilineage hematopoiesis with preserved myeloid/erythroid ratio, and normal appearing megakaryocytes. No extrinsic cells were noted. Flow cytometric analysis of the sample confirmed the presence of hematogones and detected an additional atypical population of cells within the CD45 dim blast gate. The latter accounted for up to 8% of total cells analyzed. These atypical cells expressed bright CD10, HLA-DR and CD79a. Expression of TdT and cytoplasmic IgM was dim. They were negative for CD19, CD34, CD1a, and all T and myeloid markers.
The third biopsy and aspirate smears, targeting one of the diffuse lytic bone lesions, detected extensive infiltration by a monotonous population of cells with blastoid features. Only focal areas of residual maturing hematopoiesis were noted. By immunohistochemical stains, the blastoid cells were CD10+, TdT+, CD79a+, Bcl6 dim (minor subset), LMO2+, CD19- and CD20-. Few scattered small T cells (CD3+), and smaller number of mature B cells (CD20+) were noted. By flow cytometric analysis, up to 70% and more of total events analyzed exhibited the following immunophenotype: CD45 dim, CD10+, HLA-DR+, CD38+, CD79a+, CD43+, TdT+ (dim), cytoplasmic IgM+, and largely negative for CD19, CD20, CD34, and surface immunoglobulin.CYTOGENETIC FINDINGS
Cytogenetic analyses of all samples received, including the targeted diagnostic biopsy, revealed normal karyotype (46XY) and no abnormalities by fluorescence in-situ hybridization using the ALL probe panel (TEL/AML1, MLL, BCR/ABL, p16).
MOLECULAR FINDINGS
The first and second set of bone marrow biopsy samples showed polyclonal rearrangement of the T-cell receptor (TCR) beta chain gene and immunoglobulin heavy chain (IgH) gene by polymerase chain reaction (PCR). The diagnostic biopsy detected clonal IgH gene rearrangement and polyclonal TCR beta chain gene rearrangement.
INTERESTING FEATURES
One year old male with CD19-negative B-cell acute lymphoblastic leukemia, with widespread lytic bone lesions, hypercalcemia, and essentially negative initial bone marrow iliac crest examinations.
PROPOSED DIAGNOSIS
CD19 negative B-cell acute lymphoblastic leukemia.
CONSENSUS DIAGNOSIS
B-acute lymphoblastic leukemia, with minimal CD19 expression