Therapeutic effect of nimustine in a dog with intracranial histiocytic sarcoma.

Background: Intracranial histiocytic sarcoma (HS) is uncommon in dogs, and no standard treatment has yet been defined for this disease. Herein, we describe a case of intracranial HS that responded favorably to nimustine treatment.

Case description: A 9-year-old, castrated Welsh Corgi Pembroke presented with a 2-month history of quadriplegia. Intracranial disease was suspected on neurological examination, and magnetic resonance imaging (MRI) revealed a contrast-enhanced mass in the left frontal lobe. Following tissue biopsy, the patient received intravenous nimustine (ACNU) treatment. The patient's neurological symptoms partially improved, and a reduction in tumor volume was observed on MRI on day 99. After three administrations of ACNU, tumor regrowth was confirmed on day 124, and temozolomide was subsequently administered. The patient subsequently showed no major changes in clinical symptoms, but subsequently died suddenly on day 195.

Conclusion: In this case, administration of ACNU provided temporary symptom improvement and tumor reduction. Therefore, ACNU monotherapy may be a therapeutic option for canine intracranial HS.