Primary Orbital Histiocytic Sarcoma in a Child Successfully Treated With Multiagent Chemotherapy.

Histiocytic sarcoma (HS), a malignant proliferation of mature tissue histiocytes presenting with single or multifocal extranodal tumors, is rarely seen in children. Primary orbital HS has never been reported in a child. Disseminated disease to the bone marrow typically has an aggressive course and poor prognosis. There is no consensus currently on the optimal therapeutic approach for HS. We present the case of a 2-year-old girl with orbital HS with likely bone marrow involvement treated successfully with multiagent chemotherapy, now in complete remission and disease free 3.5 years from end of therapy.