ALK-positive histiocytosis with disseminated disease responded to alectinib: a case report

: ALK-positive histiocytosis is a rare malignancy which was first described in 2008 and recognized as systemic histiocytic disorder that can affect multiple organs. Less than 20 cases were reported to date, much fewer presented disseminated disease, especially with lung central nervous system (CNS) involvement. The clinical presentation, cytologic histologic features diverse prior cases. Diagnosis relied on clinical, pathological findings might be determined by molecular identification of anaplastic lymphoma kinase (ALK) gene translocation. Exclusion other tumors such Erdheim-Chester Langerhans cell (LCH) sarcoma are required. Because their rarity features, no standard treatment applied so far. Here we 51-year-old Asian female patient documented lung, intracranial lymph nodes Surgery for left frontal tumor resection performed. Of note the presence foam-like histiocytes, epithelioid cells Touten-like histiocytes scattered lesion, emperipolesis also could observed. Histiocytes positive immunostaining CD68/PGM-1, CD163 ALK1 cytoplasmic pattern. Fluorescence situ hybridization (FISH) analysis confirmed ALK translocation next generation sequencing (NGS) revealed KIF5B-ALK fusion. received second-generation inhibitor-alectinib after diagnosed showed durable remission. Therefore, our case highlights new option this entity.