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 .
neuron - specific enolase ( nse ) , the -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
, we report on a neonate who presented with massive hepatomegaly and increased nse levels and was misdiagnosed with congenital neuroblastoma .
the patient was the second daughter of healthy and non - consanguineous japanese parents , born at 38  weeks of gestation following an uncomplicated pregnancy , and her body weight was 3164  g. at birth , she was found to have abdominal distension .
peripheral blood analysis demonstrated thrombocytopenia with a platelet count of 32    10/l .
laboratory investigations revealed the following : total bilirubin of 8.8  mg / dl , direct bilirubin of 0.7  mg / dl , lactate dehydrogenase of 2942  iu / l , aspartate aminotransferase of 248  iu / l , alanine aminotransferase of 66  iu / l , -glutamyl transpeptidase of 222 
iu / l , blood urea nitrogen of 4  mg / dl and creatinine of 0.3  mg / dl .
serum nse level was extremely high ( 1050  ng / ml ; normal value < 25  ng / ml ) and -fetoprotein was 59,540  ng / ml ( within the normal range of age - matched controls ) .
immunophenotyping and karyotyping of the bone marrow sample could not be examined because of the very small size of the sample .
arrows indicate blast cells with large nuclei and basophilic cytoplasm ( may  giemsa staining , original magnification 1000 ) .
an initial diagnosis was made of neuroblastoma stage 4s with an unknown primary lesion , although urine vma and hva levels were normal .
however , she died of pulmonary hemorrhage 1  day after therapy . abdominal mri imaging .
reverse transcriptase - polymerase chain reaction ( rt - pcr ) assay for the detection of rbm15-mkl1 fusion transcripts was performed in a not bone marrow , but liver sample with forward primer rbm15-s ( 5-ttcctcagctgcatcagaca-3 ) located in rbm15 exon 1 ( genbank accession no .
nm_022768.4 ) and reverse primers mkl1-as ( 5-tcattgaggtcatcggctag-3 ) and mkl1-as2 ( 5-tcattgaggtcatcggctag-3 ) located in mkl1 exon 7 ( genbank accession no .
pcr amplifications were performed using the qiagen one - step rt - pcr kit ( qiagen gmbh , hilden , germany ) , in accordance with a previously published protocol 7 .
sequence analysis was directly performed on the amplified rt - pcr product by using bigdye terminator cycle sequencing chemistry ( applied biosystems , foster city , ca ) on an automated sequencer abi prism 310 genetic analyser ( applied biosystems ) , in accordance with the manufacturer 's instructions .
the patient was the second daughter of healthy and non - consanguineous japanese parents , born at 38  weeks of gestation following an uncomplicated pregnancy , and her body weight was 3164  g. at birth , she was found to have abdominal distension .
peripheral blood analysis demonstrated thrombocytopenia with a platelet count of 32    10/l .
laboratory investigations revealed the following : total bilirubin of 8.8  mg / dl , direct bilirubin of 0.7  mg / dl , lactate dehydrogenase of 2942  iu / l , aspartate aminotransferase of 248  iu / l , alanine aminotransferase of 66  iu / l , -glutamyl transpeptidase of 222 
iu / l , blood urea nitrogen of 4  mg / dl and creatinine of 0.3  mg / dl .
serum nse level was extremely high ( 1050  ng / ml ; normal value < 25  ng / ml ) and -fetoprotein was 59,540  ng / ml ( within the normal range of age - matched controls ) .
immunophenotyping and karyotyping of the bone marrow sample could not be examined because of the very small size of the sample .
arrows indicate blast cells with large nuclei and basophilic cytoplasm ( may  giemsa staining , original magnification 1000 ) .
an initial diagnosis was made of neuroblastoma stage 4s with an unknown primary lesion , although urine vma and hva levels were normal .
however , she died of pulmonary hemorrhage 1  day after therapy . abdominal mri imaging .
reverse transcriptase - polymerase chain reaction ( rt - pcr ) assay for the detection of rbm15-mkl1 fusion transcripts was performed in a not bone marrow , but liver sample with forward primer rbm15-s ( 5-ttcctcagctgcatcagaca-3 ) located in rbm15 exon 1 ( genbank accession no .
nm_022768.4 ) and reverse primers mkl1-as ( 5-tcattgaggtcatcggctag-3 ) and mkl1-as2 ( 5-tcattgaggtcatcggctag-3 ) located in mkl1 exon 7 ( genbank accession no .
pcr amplifications were performed using the qiagen one - step rt - pcr kit ( qiagen gmbh , hilden , germany ) , in accordance with a previously published protocol 7 .
sequence analysis was directly performed on the amplified rt - pcr product by using bigdye terminator cycle sequencing chemistry ( applied biosystems , foster city , ca ) on an automated sequencer abi prism 310 genetic analyser ( applied biosystems ) , in accordance with the manufacturer 's instructions .
, there were multiple nodules composed of diffuse proliferation of small round cells in the liver ( fig.3a ) .
immunohistochemically , the proliferating cells were positive for cd41 , cd42b , cd43 , and nse , but negative for myeloperoxidase , tdt , cd7 , cd68 , cd163 , pgp9.5 , and tyrosine hydroxylase ( fig.3b ) .
fluorescence in situ hybridization revealed chromosome 21 disomy , indicating that the patient did not have down syndrome .
atypical cells are observed in the liver ( hematoxylin and eosin staining  left panel : original magnification 200 ; right panel : original magnification 1000 ) .
the lesion is positive for nse ( left panel ) and cd41 ( right panel ) ( original magnification 200 ) .
lanes 1 , 2 and 4 indicate a 100-bp molecular marker , an internal control , and a negative control , respectively .
( b ) sequence analysis of the amplified rt - pcr product revealed an in - frame fusion between rbm15 exon 1 and mkl1 exon 5 .
leukemia occurs much less frequently in the perinatal period than in later childhood . although not as common as neuroblastoma , leukemia is the leading cause of death due to neoplastic disease in neonates 8 .
many cases of congenital neoplasms do not present with overwhelming signs and symptoms , and rapid and accurate diagnosis may be difficult .
amkl is a rare variant of aml , and the leukemic blasts show characteristic morphologic and phenotypic features , indicating megakaryocytoid differentiation . a distinct entity characterized by t(1 ; 22)(p13;q13 ) , resulting in the rbm15-mkl1 fusion oncogene
, has recently been identified . of the recognized subtypes of amkl , the disease associated with t(1;22 )
has clinicopathologic features that present in neonates and infants and is frequently associated with abdominal organomegaly 3,9 .
the liver was involved as the primary site in some patients with congenital leukemia 9 .
neonates with down syndrome sometimes present transient myeloproliferative disorder mimicking amkl 10 ; however , this patient was not diagnosed with down syndrome . at the initial evaluation ,
, the elevation of serum nse level and a few and absent blastic cells in the bone marrow and the peripheral blood might have led to a clinical misdiagnosis .
nse is usually synthesized by neurons and neuroendocrine cells , and it is a useful marker for the diagnosis and monitoring of patients with neuroendocrine tumors such as neuroblastoma and small cell lung cancer 11 .
however , nse is found not only in neuroendocrine cells but also in other cells including erythrocytes and subsets of lymphocytes 4,5 .
some of the hematopoietic cell lines including t - cell leukemia and epstein  barr virus - immortalized b lymphoblastoid cell lines produce nse .
thus , nse is not exclusively expressed in neuroendocrine tumor cells 12 . in the present case ,
the fibrosis might have been caused by the production and secretion of transforming growth factor beta from the megakaryoblasts , which stimulates collagen synthesis in bone marrow fibroblasts 13 .
there are very few documented cases of congenital leukemia in which the primary site of involvement was shown to be the liver , without initial bone marrow findings .
a case of congenital anerythremic erythroleukemia was reported to present with hepatic failure and have a fetal outcome of multivisceral involvement 14 .
an infant with amkl and a complex translocation demonstrated only 520% blasts on the initial bone marrow aspirate and core biopsy .
therefore , myelodysplastic syndrome was initially diagnosed ; however , only later did blasts become apparent in the peripheral blood 15 . in the present case , amkl might have occurred in the fetal period because hematopoietic cells are mainly produced in the fetal liver . here , we report on a neonate who presented with massive hepatomegaly , increased serum nse levels , and was misdiagnosed with congenital neuroblastoma .
 key clinical messagewe describe a neonate with abdominal distension , massive hepatomegaly , and high serum neuron - specific enolase level suggestive of congenital neuroblastoma . 
 the patient died of pulmonary hemorrhage after therapy . 
 autopsy revealed that the tumor cells in the liver indicated acute megakaryocytic leukemia with the rbm15-mkl1 fusion gene . 