Long-Term Survival of Primary Intracranial Histiocytic Sarcoma Through Surgical Resection and Low-Dose CCNU

A 5 yr old chihuahua presented to our clinic with a complaint of decreased activity and focal seizures. Based on the findings of MRI and computed tomography, a primary brain tumor originating from the right frontal lobe region was suspected. Surgical resection was performed, and a diagnosis of histiocytic sarcoma was made via histopathological examination and immunohistochemical staining. Low-dose 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) (45 mg/m2 every 4-5 wk) was started postoperatively, and no apparent recurrence was found on two MRI scans until the patient's death on day 359. We hypothesized that long-term survival might be achieved in dogs with solitary histiocytic sarcoma of the central nervous system with no metastatic lesions at diagnosis by combining local treatment with CCNU. We also suggested that CCNU may effectively suppress the recurrence of histiocytic sarcoma, even at low doses.