Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm with intermediate malignant potential, typically occurring in children and young adults. We report a case of seven-year-old boy with a well-defined, extra-articular medial knee mass. MRI demonstrated a solid lesion with strong homogeneous enhancement without joint or bone invasion. Complete surgical excision was performed. Histopathology revealed myofibroblastic spindle-cell proliferation in a myxoid stroma with mixed inflammatory infiltrate. Immunohistochemistry showed SMA positivity and ALK negativity; molecular testing identified ROS1 rearrangement and COL1A1-PDGFRa fusion. The postoperative course was uneventful with no recurrence on follow-up. This case underscores the value of comprehensive molecular profiling in atypical IMT locations and the potential for targeted therapy in unresectable or recurrent disease.
Janković et al. (2025) studied this question.