How do you approach treatment of recurrent histiocytic sarcoma in a young, healthy patient after surgical resection?

HS is a very rare type of malignant histiocytosis with dismal outcomes for multifocal disease. Given the rarity, there are very little data on the management of this disease, and management approaches are based on anecdotal and small retrospective experiences.

For unifocal disease that can be entirely resected, no further intervention may be needed. However, it is important to monitor the patient closely and perform surveillance imaging (pref. FDG PET-based). Systemic chemotherapy regimens borrowed from lymphoma or sarcoma are mostly suboptimal. Consider NGS for somatic alterations that can help with targeted therapies (BRAF, MEK, CSF1R, etc.). Consider referral to a histiocytosis clinic early.