Durable response to brigatinib in a ROS1 fusion-positive inflammatory myofibroblastic tumor.

Inflammatory myofibroblastic tumor is an ultra-rare mesenchymal neoplasm of intermediate malignant potential, characterized by oncogenic rearrangements involving ALK (50–60%), ROS1 (5–10%), and less commonly NTRK3 or RET. We report a 32-year-old woman with an unresectable pulmonary tumor harboring a TFG–ROS1 fusion who achieved a durable partial response to brigatinib, sustained for more than 12 months. Histopathologic evaluation revealed a low-grade spindle-cell neoplasm lacking ALK expression, and genomic profiling identified the actionable fusion. This case highlights how molecular characterization can refine the management of ultra-rare sarcomas, enabling anatomically constrained disease to become targetable and underscoring the role of tumor biology in therapeutic decision-making.