Justin Oh

Key Clinical Message Langerhans cell histiocytosis (LCH) is a rare inflammatory myeloid neoplasm arising from the proliferation of pathologic Langerhans cells. LCH has a spectrum of presentations predominantly affecting male pediatric patients. As LCH is a relatively uncommon diagnosis, there is no standard of care for treatment of the disease and treatment is based largely on clinical judgment, lesion characteristics, and symptoms at presentation. Here we present a case of unifocal, isolated orbital LCH in a 19‐year‐old young man treated initially with surgical resection. Follow‐up imaging 2 months later demonstrated significant regrowth of the mass and no other sites of disease. The recurrent orbital disease was treated with stereotactic radiosurgery (SRS) to 7 Gy in one fraction. Near complete resolution of the mass was achieved with no recurrence after 1.5 years of follow‐up. SRS for treatment of orbital LCH is a novel treatment not previously described in the literature which may provide benefit in select cases.