ALK-positive Histiocytosis of Umbilicus Subcutaneous with KIF5B-ALK Fusion: a Case Report

Background: Since the discovery of the first case of Anaplastic lymphoma kinase (ALK) -positive histiocytosis in 2008, originally described as a systemic, self-limiting disease in infants, the range of ALK-positive histiocytosis has recently been expanded to include localized diseases in older children and young adults. Case presentation: We present the case of an 18-year-old female with periumbilical painless mass for 5 months, who underwent a resection of the mass. Pathological examination showed the tumor consists predominantly of fascicular to storiform growth of nonatypical spindle cells, admixed with lymphocytic infiltrates. The tumor spindle cells were diffusely positive for CD68, CD163 and ALK. Further, molecular tests revealed ALK gene fusion: Kinesin Family Member 5B (KIF5B) (E24)-ALK (E20), confirmed ALK-positive histiocytosis. The tumor has not recurred one and a half years after resection by follow-up examination. Conclusion: ALK-positive histiocytosis in local lesion can achieve remission by complete resection and clinical follow-up showed a favorable prognosis.