Glomus Tumor in the Femoral Nerve
A 56-year-old man presented with severe lancinating pain at left anterior thigh for nine years, one year after accidentally bumping his left thigh to a tree. The pain worsened over time and he eventually limped for five years. He initially visited the other medical center where he was diagnosed with a mass lesion in the left thigh. Surgical exploration was performed, which was unsuccessful, and the pain persisted. The effect of direct lidocaine injection was temporary and unsatisfactory. He was referred to the neurosurgery department for evaluation and surgical management.\nOn physical examination, severe direct tenderness in the left anterior thigh was observed. His left thigh was rather atrophic compared to the right side. The range of motion in the extremities was full, but pain was provoked by physical irritation or by knee extension. The pain graded by the Visual Analog Scale was 10. Motor weakness or radiating pain in the leg was not distinct. Electromyography (EMG) and nerve conduction velocity were consistent with left femoral neuropathy of moderate degree and chronic partial axonotmesis state. The defect was most severe at the branch leading to the vastus lateralis.\nThe magnetic resonance images showed a well-defined, enhancing mass of 2.5 cm in diameter at left mid-thigh level, in between the rectus femoris, vastus laterlis, and vastus intermedius muscles (). The mass was formed along a muscular branch of the femoral nerve, and thus resembled a neurogenic tumor of femoral nerve branch, such as schwannoma. The initial differential diagnoses before operation were schwannoma or post-traumatic painful neuroma.\nThe patient underwent surgical exploration and gross total resection was done under spinal anesthesia. Intraoperative ultrasonography was used to localize the mass (). The tan, pinkish white tumor was oval in shape with moderate vascularity, and well demarcated with the nerve tissue ().\nThe pathological findings were compatible with benign glomus tumor. The tumor cells were basophilic, round and fairly uniformed. They had rich cytoplasm and centrally placed nuclei. The cellular borders were sharply defined and angulated, and dilated vessels were surrounded by the tumor cells. The immunohistochemical staining showed positive for smooth muscle antigen (SMA) and negative for S-100 protein, and the Ki-67 proliferative index was less than 1.0% ().\nPostoperatively, the patient's symptom improved dramatically. The sharp pain was completely resolved and new neurological deficit was not observed. No evidence of recurrence or pain was noted at 24 months after resection.