Neonatal acute megakaryoblastic leukemia mimicking congenital neuroblastoma

Acute megakaryoblastic leukemia (AMKL) with t(1;22)(p13;q13) represents <1% of all acute myeloid leukemias (AML), and is associated with the RBM15 (OTT)-MKL1 (MAL) fusion gene. It occurs at higher incidence in the pediatric population and accounts for approximately 70% of infants with AMKL 1,2. In contrast to infants with 11q23-associated leukemia who frequently exhibit hyperleukocytosis, those with RBM15-MKL1 fusion-positive AMKL usually present with decreased leukocyte count, severe anemia, and thrombocytopenia. The pathological findings show fibrosis along with the leukemic cells in the bone marrow and lymph node 3. AMKL with t(1;22)(p13;q13) is a rare disease that is often associated with massive organomegaly. Therefore, it may be misdiagnosed as solid organ tumors including hepatoblastoma and neuroblastoma. Neuron-specific enolase (NSE), the γ-subunit of enolase, is found not only in neuroendocrine cells but also in other cells including erythrocytes and subsets of lymphocytes 4,5. Increased levels of serum NSE were reported in several patients with acute lymphoblastic leukemia 6. Here, we report on a neonate who presented with massive hepatomegaly and increased NSE levels and was misdiagnosed with congenital neuroblastoma. Autopsy revealed that the patient was finally diagnosed with RBM15-MKL1 fusion-positive AMKL.