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Unexpected Epithelial Membrane Antigen (EMA) and Cytokeratin Expression in a Case of Infantile Acute Monoblastic
S K Cheong1, S F Chin1, O Azizon1
1a Haematology Unit, Faculty of Medicine, Universiti Kebangsaan Malaysia , Kuala Lumpur.
Insights
This case study highlights an infant diagnosed with acute monoblastic leukemia (FAB M5a). Monoblasts unexpectedly expressed epithelial membrane antigen (EMA) and cytokeratin, crucial for differential diagnosis in neoplastic diseases.
Area of Science:
- Hematology
- Pediatric Oncology
- Immunophenotyping
Background:
- Acute monoblastic leukemia (FAB M5a) can present with extramedullary infiltration.
- Infants may exhibit unusual symptoms like fever, respiratory infections, and swelling.
- Accurate immunophenotyping is critical for diagnosing leukemia subtypes.
Purpose of the Study:
- To report a rare case of acute monoblastic leukemia in an infant.
- To investigate the immunophenotype of blast cells, including unexpected marker expression.
- To emphasize the importance of considering monoblast expression of EMA and cytokeratin in differential diagnoses.
Main Methods:
- Clinical presentation and physical examination of an eleven-month-old infant.
- Diagnostic investigations including flow cytometry for immunophenotyping.
- Evaluation of blast cell expression of CD markers, EMA, and Cytokeratin.
Main Results:
- The infant was diagnosed with acute monoblastic leukemia (FAB M5a).
- Blast cells showed positivity for CD45, CD13, CD33, HLA-DR, CD11c, CD71, EMA, and Cytokeratin.
- Unexpected positivity for EMA and Cytokeratin in monoblasts was observed.
Conclusions:
- Monoblasts can express EMA and Cytokeratin, which is important for differential diagnosis.
- Extramedullary infiltration is a common presentation of acute monoblastic leukemia.
- This case underscores the need to consider atypical marker expression in leukemia diagnosis.
Abstract:
A previously healthy eleven month old male Malay infant presented with fever, upper respiratory tract infection and right knee swelling. Pallor, bilateral proptosis, hepatosplenomegaly, multiple scalp swellings and a right cheek swelling were observed. Investigations revealed that he had acute monoblastic leukemia or FAB M5a. Immunophenotyping by flow cytometry showed that the blast cells were positive for CD45, CD13, CD33, HLA-DR, CDllc, CD71, EMA, and Cytokeratin. They were negative for CD34, CD19, CD10, CD22, CD2, CD3, CD4, CD7, CD8, CD61, NK, Glycophorin A, and CD14. The monoblasts were used to evaluate anti-EMA and anti-cytokeratin. They were unexpectedly found to be positive. Acute monoblastic leukaemias are well known to show extramedullary infiltration and this may be their primary mode of presentation. Thus, in immunochemostry, when using EMA and cytokeratin expression in the differential diagnosis of neoplastic diseases, it is important to consider that monoblasts may express these markers as illustrated by this case.
