RARE-13. INFLAMMATORY MYOFIBROBLASTIC TUMOR MIMICKING DESMOPLASTIC INFANTILE GANGLIOGLIOMA (DIG) OF THE TEMPORAL LOBE

Abstract Inflammatory myofibroblastic tumor (IMT) is a mesenchymal neoplasm composed of fascicles of myofibroblastic spindle cells in a background of prominent inflammatory infiltrate. It is categorized as ‘intermediate, rarely metastasizing’ in the World Health Organization classification of tumors of soft tissue and bone. We present a novel case of concurrent brain and lung tumor with diagnosis of TFG-ROS1-rearranged IMT in a 14 year old female patient, in which targeted next-generation sequencing became a powerful tool for detection of genomic alterations in both lung and brain tumors. At age 9, the patient’s lung mass was incidentally found and investigated for various infectious diseases with negative result. At age 14, she presented with seizure and was noted to have a stable size lung mass and a left temporal lobe tumor. The left temporal lobe tumor showed a desmoplastic spindle cell neoplasm involving the meninges and cerebral cortex and Desmoplastic Infantile Ganglioglioma (DIG) was considered one of differentials. Subsequently, her right lung mass was resected and showed a similar spindle cell neoplasm with a background of dense fibrosis and chronic inflammation, consistent with Inflammatory Myofibroblastic Tumor. Molecular microdissection revealed that both tumors shares TFG-ROS1 fusion which is associated with (t(3;6) (q12;q22)), thus it is strongly suggestive that two tumors arose from the same origin. No predisposition syndrome was identified.