Concurrence of Malignant Peripheral Nerve Sheath Tumor at the Site of Complex Regional Pain Syndrome Type 1 - A Case Report -
A 44-year-old female patient was referred to our pain clinic due to persistent pain in the lateral side of the left ankle even after conservative treatment for 5 months. The pain developed after frequent ankle sprains and a splint was applied 1 year prior to her visit. For her medical history, she had received surgical treatment for neurofibromatosis 20 years ago. The pain intensity was 10/10 on the visual analogue scale (VAS), and the nature of the pain was squeezing, bursting and tingling. The patient showed allodynia and hyperalgesia in her left ankle and there was edema, skin color change and trophic change of the skin. We carried out various examinations including left ankle MRI, bone scan, autonomic nervous system function test, quantitative sensory test, electro-diagnostic study and diagnosed her as CRPS type 1.\nAfter the CRPS diagnosis, we carried out various treatments including oral medications, lumbar sympathetic ganglion block, and common peroneal nerve block. After these treatments for 8 months, the edema and allodynia decreased, and the pain intensity was 4-6/10 on the VAS. Because there was some improvement in her symptoms, she did not come to our hospital and instead received treatment at an oriental herbal medicine clinic.\nSix months later, she re-visited our pain clinic again because of aggravated pain in her left ankle. She complained of aggravated pain, numbness in her left ankle and difficulty in walking. Additionally, she stated there was a mass-like lesion in her left lower leg. Therefore, we conducted ultra-sonography, and there was a 2.7 × 2.7 × 4.3 cm mass with heterogeneous echogenicity at the posterior aspect of the left thigh (). Moreover, an electromyography and nerve conduction study (EMG-NCS) showed newly developed left sciatic neuropathy (more severely involved in the peroneal division than the tibial division), which had been normal 14 months prior to her visit. Left thigh MRI showed about a 3.0 × 3.1 × 5.2 cm sized mass along the common peroneal nerve in the left posterior thigh (), and US-guided biopsy diagnosed the mass as a malignant peripheral nerve sheath tumor. Positron emission tomography (PET) examination of the whole body was performed in order to rule out any possible metastasis and PET showed a lesion that was suggestive of lymph node metastasis in the thoracic region.\nTherefore, she was transferred to an orthopedic and thoracic surgeon, and complete mass excision at the posterior thigh and mediastinal lymph node dissection were performed with video-assisted thoracic surgery. The durgical specimen containing a solid mass measuring 4.0 × 3.5 × 3.5 cm () was proven to be MPNST. After the surgery, the numbness and pain decreased. And the patient received chemotherapy and radiation therapy.