Rare Case of Mixed Phenotype Acute Leukemia Presenting as a Myeloid Sarcoma Without Leukemic Involvement.

INTRODUCTION

Mixed phenotype acute leukemia (MPAL) is a rare type of acute leukemia with immunophenotypic features of both myeloid-derived and lymphoid-derived lineages.

CASE PRESENTATION

We present an atypical case of a 32-year-old woman presenting with an anterior mediastinal mass and pericardial/pleural involvement that was initially diagnosed as primary mediastinal diffuse large B-cell lymphoma. However, flow cytometry on pleural fluid confirmed the diagnosis of MPAL of B-cell/myeloid lineage without peripheral blood/bone marrow involvement. The patient was treated with an acute lymphoblastic leukemia-type regimen and proceeded with myeloablative allogeneic hematopoietic cell transplantation in first complete remission.

CONCLUSION

MPAL can rarely present with isolated extramedullary disease without leukemic involvement and can often be misdiagnosed as a non-Hodgkin lymphoma. Careful integration of all the clinical data, particularly flow cytometry results, can clarify the diagnosis and change the treatment plan.