Acute myeloid leukaemia masquerading as a primary CNS tumour

In children with newly diagnosed acute myeloid leukaemia (AML), myeloid sarcomas (MS) of the central nervous system (CNS) are rare. Since MS involving the CNS are potentially curable, timely recognition is paramount. Establishing a diagnosis may be problematic as they can easily mimic primary CNS neoplasms. We report the case of a 5-year-old boy with AML with t(8;21)(q22;q22) rearrangement who presented with a massive intracranial MS and rapid clinical deterioration suggestive of a meningioma or a primitive neuroectodermal tumour. The peripheral smear showed blasts with Auer rods. Urgent chemotherapy was started for AML with presumptive CNS MS. The mass resolved with chemotherapy, and treatment was consolidated with radiotherapy. Although exceedingly rare, this case highlights the potential for MS to present similarly to a primary CNS tumour. MS should be part of the differential diagnosis as part of a CNS mass, particularly if the complete blood count is abnormal.