Korean J Lab Med.  2007 Aug;27(4):253-256. 10.3343/kjlm.2007.27.4.253.

A Case of CD45-, CD19- Precursor B Cell Acute Lymphoblastic Leukemia with an Atypical Morphology

• Moon H
• Huh J
• Cho MS
• Chi H
• Chung WS

• KMID: 1781493
• DOI: http://doi.org/10.3343/kjlm.2007.27.4.253

Abstract

The differential diagnosis of acute lymphoblastic leukemia (ALL) from other small round blue cell tumors in children is very important for proper treatment, but sometimes difficult. CD45 is expressed on almost all-human leukocytes and not expressed on other small round blue cell tumors. Moreover, CD19 is expressed on all stages of B lineage cells and loss of this antigen is very rare in precursor B-cell ALL. We report a case of ALL with atypical morphology and immunophenotype. A 6-yr-old girl presented with fever and weight loss. Many abnormal cells with variable sized, high nuclearcytoplasmic ratio and distinct nucleoli were counted 23% in bone marrow. The results of immunophenotyping were negative for CD45, CD19, CD10, CD20, CD3, CD5, CD7, CD56/16, CD13, and CD33 and positive for CD22, TdT, and CD34. The immunohistochemical staining of bone marrow biopsies was positive for CD79a, CD10, TdT and CD99. The cytogenetic study showed normal karyotype but amplification of MLL (myeloid/lymphoid or mixed lineage leukemia) gene was suggestive in the fluorescent in situ hybridization. The patient received the standard chemotherapy for acute lymphoblastic leukemia and reached complete remission.

Keyword

CD45; CD19; Acute Lymphoblastic Leukemia

MeSH Terms

Acute Disease
Antigens, CD19/*analysis
Antigens, CD45/*analysis
Bone Marrow/*pathology
Child
Female
Humans
In Situ Hybridization
Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/diagnosis/*pathology

Figure

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  Fig. 1. Bone marrow findings showed many abnormal cells with highly variable sizes, a high nuclear-cytoplasmic ratio, fragile cytoplasm, and loose chromatin (A). Dysplastic changes were present in myeloid and erythroid series (B). Megakaryocytes showed dysplasia, e.g., separated nucleation (C). A biopsy showed scattered immature cells and an increased megakaryocyte count (D).

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  Fig. 2. The results of immunophenotyping. Leukemic cells were negative for CD19 and CD45 and positive for TdT, CD22, HLA-DR and CD34.

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  Fig. 3. Fluorescent in situ hybridization study using an MLL probe showed three fusion signals.

Reference

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