Epithelioid malignant peripheral nerve sheath tumor: a case report and review of literature

Abstract

Background Epithelioid malignant peripheral nerve sheath tumor (EMPNST) is a rare malignant soft tissue tumor, and is more common in adult male. EMPNST originates from nerve, mainly located in the limbs, head and neck, and spine. It is an aggressive tumor with high tendency for local recurrence, and about half of the cases appear distant metastasis. This paper aims to investigate the clinicopathological features of cervial EMPNST. Methods and Results A 48-year-old male mainly presented weakness of limbs, expecially left lower extremty with ankle swelling. MRI showed space-occupying lesion in segment C3-5, considering recurrence of intraspinal tumor 2 years after operation. Tumor resection, repairing of spinal dura mater and laminectomy were made from inion to C7 level. It was found during the surgery that most part of the tumor was located in front of C3-5 spinal nerve, left intraspinal and outside of dura mater. Because part of the tumor grew through the opening of titanium plate, the tumor could not be totally removed. According to postoperative histomorphological observation, tumor cells arranged in sheets or nests, and were separated by fibrous tissue. Most tumor cells were epithelioid, while small part of tumor cells were fusiform. Frequent mitotic activity was found, and part of the region appeared focal necrosis. Immunohistochemical staining showed that tumor cells were positive for pan cytokeratin (PCK), epithelial membrane antigen (EMA), vimentin (Vim), synaptophysin (Syn), chromogranin A (CgA), and S-100 protein (S-100); and were negative for actin, desmin (Des), progestrone receptor (PR), glial fibrillary acidic protein (GFAP), CD34, CD31 and HMB45; Ki-67 labeling index was above 25% . Reticular fiber staining showed that the epithelioid cell nests were surrounded by reticular fibers. Fluorescence in situ hybridization (FISH) detection showed negative for SS18 gene translocation. Combining with the history, the final pathological diagnosis was cervical EMPNST. Conclusion EMPNST lacks of morphological characteristics, and needs to be differentiated from a variety of benign or malignant tumors exhibiting epithelioid features. It is considered that clinical materials, morphological features and immunophenotype are helpful to avoid confusion with other similar lesions. S-100 is not a specific marker, but is a valuable diagnostic index. PCK and EMA can present strongly positive expression. doi：10.3969/j.issn.1672-6731.2013.11.008