ALK-positive histiocytosis in 12 Asian children.

Anaplastic lymphoma kinase-positive histiocytosis, first reported in 2008, is a rare, novel type of neoplasm. To date, no more than 100 cases of anaplastic lymphoma kinase-positive histiocytosis have been reported. In this retrospective study, 12 cases of anaplastic lymphoma kinase-positive histiocytosis, including clinical symptoms, histological features, molecular pathology, treatment, and prognosis, in children were analyzed to gain a deeper understanding of the disease. All patients were Asian children, aged 2 months to 8 years and 2 months (mean 3.1 years), and the male-to-female ratio was 5:7. All patients were followed up closely. One patient died during the follow-up period, seven (case 1-7) had focal anaplastic lymphoma kinase-positive histiocytosis, and five (case 8-12) had multisystem anaplastic lymphoma kinase-positive histiocytosis. In addition, we report the case of a patient who benefited from anaplastic lymphoma kinase-targeted therapy and a patient with the rare EML4-ALK fusion gene. The current study is expected to substantially contribute to increasing the awareness of anaplastic lymphoma kinase-positive histiocytosis.