Comparison of Clinical, Histopathological, and Genomic Features Between Malignant Peripheral Nerve Sheath Tumors and Cellular Schwannomas of the Eighth Cranial Nerve: A Case Series.

Background: Malignant peripheral nerve sheath tumors (MPNSTs) and cellular schwannomas (CSs) of the eighth cranial nerve are exceedingly rare. The purpose of the present study was to evaluate clinical and genetic characterization of these rare tumors.

Methods: The clinical and radiological features were analyzed retrospectively. The histopathological characteristics were assessed by hematoxylin and eosin staining and immunohistochemistry. Genomic abnormalities were evaluated using array comparative genomic hybridization.

Results: Of the 1287 surgeries for vestibular schwannomas from 2014 to 2017, 2 were for MPNSTs and 5 were for CSs. The mean age at diagnosis was older for patients with MPNSTs (57.0 ± 4.2 years) than that of patients with CS (35.8 ± 9.4 years; P = 0.03). Two patients with MPNST died of tumor recurrence. None of the patients with CS died. The 2-year overall and progression-free survival of patients with MPNSTs were worse than those for patients with CSs (overall survival, 50.0% ± 35.4% vs. 100%, P = 0.027; progression-free survival, 0% vs. 100%; P = 0.012). The Ki-67 index for the MPNSTs (29.0% ± 3.5%) was greater than that for the CSs (10.3% ± 3.1%; P = 0.001). The common alterations in MPNSTs mainly included gains of chromosomes 7p, 8p, 9q, 12, and 17 and loss of heterozygosity of 1p, 6 and 9p. The common alterations in CSs included gain of 4p16.3, loss of heterozygosity of 2p15-14, and 22q11.1-13.3.

Conclusions: To the best of our knowledge, the present study is the first high-resolution genomic analysis of MPNSTs and CSs of the eighth cranial nerve and has shown a significant difference that might be more accurate to distinguish between these 2 types of rare tumors.