SOFT TISSUE MASS AND ELECTRICAL DISCHARGE: WHATS INVOLVED?

An 11-year-old girl presented with a gradually evolving, painful arm mass over 6 months. Clinical examination revealed a 4cm soft mass causing electric discharge pain on percussion, without signs of inflammation. Ultrasound depicted a well-defined, heterogeneous mass connected to the median nerve with moderate vascularization. Subsequent MRI showed an eccentric fusiform mass within the median nerve, exhibiting a muscle-like signal on T1-weighted images, a heterogeneous signal on STIR, and enhancement after contrast. No bony destruction or muscle invasion was observed. Peripheral nerve sheath tumors, including neurofibromas and schwannomas, were suspected. MRI played a crucial role, revealing characteristic signs like split fat, target, and fascicular signs, aiding in distinguishing between benign and malignant lesions. Intra-tumoral changes, like cystic degeneration seen in schwannomas, were noted. Malignant tumors, such as MPNSTs, showed distinct features like increased size, heterogeneous appearance, perilesional edema, and bony destruction. In summary, the patients arm mass, initially detected through ultrasound and further characterized by MRI, raised concern for peripheral nerve sheath tumors, highlighting the significance of imaging in diagnosing and distinguishing these lesions.