Inflammatory Myofibroblastic Tumor of the Knee  in a 7-year-old Child: A Case Report

Aleksandar Janković; Zoran Marjanović; Nikola Bojović; Nikola Vacić; Dejana Božić

doi:10.5937/medrec2504096J

Aleksandar Janković Clinic for Pediatric Surgery, Orthopedics and Traumatology, University Clinical Center Niš, Niš
Zoran Marjanović Clinic for Pediatric Surgery, Orthopedics and Traumatology, University Clinical Center Niš, Niš https://orcid.org/0000-0002-0929-686X
Nikola Bojović Clinic for Pediatric Surgery, Orthopedics and Traumatology, University Clinical Center Niš, Niš https://orcid.org/0000-0003-0357-6833
Nikola Vacić Clinic for Pediatric Surgery, Orthopedics and Traumatology, University Clinical Center Niš, Niš https://orcid.org/0000-0002-6826-1747
Dejana Božić Institute for Health Protection of Mother and Child “Dr Vukan Čupić”, Belgrade https://orcid.org/0009-0002-3527-0847

DOI: https://doi.org/10.5937/medrec2504096J

Keywords: inflammatory myofibroblastic tumor, knee, child, ROS1, PDGFRα, ALK-negative

Abstract

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–PDGFRα 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.

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