Mrs. Li, 73 years old, had left dorsal foot pain with dorsiflexion weakness in January, and was treated in several hospitals, but no etiology was found, and there was no improvement after neurotrophic drugs and other treatments. She was introduced by a friend to the Neurosurgery Department of Xinhua Hospital, Shanghai Jiaotong University School of Medicine, peripheral nerve disease outpatient clinic, the doctor carefully examined the body, neurological examination found that the old lady’s left popliteal fossa outside of a diameter of only 2cm “surface mass” is the main culprit. According to the medical history, this ordinary surface mass has been accompanying the old lady for nearly 10 years, with no pain and no itch, and slightly enlarged after questioning, but the old lady has always thought that this is a lipoma, and did not consult a doctor for examination. After high-frequency nerve ultrasound and MRI examination, this is a peroneal nerve sheath tumor, by the neurosurgeon under the microscope complete resection of the tumor, Mrs. Li’s symptoms completely relieved. Surface swelling is often considered a common disease, minor surgery, and then some of them are not “common”. Nerve sheath tumor is the most common peripheral nerve tumor, clinical easy to misdiagnose as ordinary soft tissue swelling, blindly mass excision surgery easy to lead to medical nerve damage. High-frequency ultrasound can be used as the first choice of imaging examination for peripheral nerve tumors, which is helpful for local diagnosis and surgical positioning.MRI can be used for further qualitative diagnosis and differential diagnosis of nerve tumors. Aggressive surgical resection should be performed after the diagnosis is clear. Minimally invasive surgery is performed under the microscope, and the sheath tumor does not invade the nerve. During the operation, the relationship between the tumor and the nerve trunk should be carefully confirmed, the tumor envelope containing the nerve periphery should be incised longitudinally along the nerve trunk, and the nerve fascia should be sharply separated longitudinally to reveal the tumor. Intraoperative combined neurophysiological monitoring can minimize the damage to the nerve during dissection, pulling and stripping of the tumor. Nerve sheath tumors often have only a single non-functional nerve bundle access, which can be resected together with the tumor without nerve reconstruction. For small to medium-sized sheath tumor, it can be resected as a whole without damaging the nerves; for larger or deeper tumors, it is feasible to resect the tumor in pieces; for tumors with cystic degeneration, the cystic fluid should be aspirated first to facilitate the exposure of the tumor. For cases with preoperative nerve entrapment symptoms, it should be ensured that there are no other soft tissue factors causing entrapment after tumor resection. The tumor-carrying nerve should be reset before closing the incision to avoid the formation of secondary entrapment, and the deep fascia may not be sutured.