We report the case of a 1-year-old male patient with systemic juvenile xanthogranuloma in whom central nervous system lesions caused developmental retardation, spasticity and clonus of the lower extremities. He needed tube feeding and experienced severe bronchitis and generalised convulsive seizure. KIF5B-ALK fusion was identified in the cutaneous lesion, and he was administered alectinib, an ALK inhibitor. Two months after the initiation of alectinib administration, the central nervous system lesions achieved partial regression. The spasticity and clonus were also relieved. A high index of cognition is needed for ALK fusion in infants with histiocytosis.

Several central nervous system complications in pediatric patients with hematological malignancies have been reported. We analyzed the frequency and the correlation with central nervous system involvement and intrathecal therapy. The frequency was 13 % (11/85), being almost equal to those in literature. We investigated high intensity areas, which indicated leukoencephalopathy, in the white matter by T2-weighted and/or fluid attenuated inversion recovery images (FLAIR) of the brain magnetic resonance imaging (MRI). Incidence of white matter lesions was higher in patients who received over 10 times of intrathecal therapy (p = 0.018). Patients who received repetitive intrathecal therapy should undergo close MRI to find out if they need cognitive functioning test. However, it may be possible to omit brain MRI in patients with acute myeloid leukemia and lymphoma who have received intrathecal therapies less than five times in a consideration of their burden in terms of sedation and cost.

Although hepatoblastoma constitutes most of hapetic tumours in chidren, other types of tumors are often observed in older patients. We report a case of a 10-year-old Japanese boy with a transitional hepatic tumour consisting of both hepatoblastoma and hepatocellular carcinoma. After surgery and chemotherapy with cisplatin and pirarubicin, the tumour regressed, however, new tumours in the liver evolved with element of hepatocellular carcinoma. He died as a result of hepatic failure afte lenvatinib and drug-eluting transcatheter arterial chemoembolisation 18 months after diagnosis. Examinations of a panel of genomic alterations did not identify any therapeutic targets.