Poster 079: A Review of 308 Oral Peripheral Nerve Sheath Tumors

Abstract

Recently we have started the classification of all oral soft tissue tumors that have been accessioned at the Oral Pathology Laboratories, University of Minnesota, School of Dentistry. We reviewed first peripheral nerve sheath tumors (PNST). In general, oral PNSTs are not infrequent and they may be occasionally associated with syndromes such as neurofibromatosis types 1, schwannomatosis, and multiple endocrine neoplasia type 2B. In this study we included neurofibromas, schwannomas, palisading encapsulating neuromas (PEN), and traumatic neuromas. Also we tried to identify unusual types of PNSTs such as myxomas, perineuriomas, neurothekeomas, etc. Granular cell tumors, although they are of apparent neural origin, were not included this time. The archives from 1959 to 2006 included 410 cases of PNSTs. From these cases we have completed the evaluation of 308. Clinicodemographic data were available in all these cases as were histologic preparations. We performed descriptive statistics. Out of 308 cases of PNSTs, 141 (∼45.8%) were neurofibromas, 74 (∼24.0%) were traumatic neuromas, 48 were (∼15.6%) schwannomas, 39 (∼12.6%) were PEN and 2 (∼0.6%) were nerve sheath myxomas. In this first cataloguing we did not include a potential case of perineurioma since the immunohistochemical evaluation is not performed yet. There were no confirmed cases of neurothekeomas. Among the 141 cases of neurofibromas, 85 (∼60.3%) patients were females and 56 (∼39.7%) males. Age ranged from 11-93 years with the mean of 41 years. The location was known for 139 cases. Specifically, 35 (∼25%) occurred in the palate, 28 (∼20%) on the mandibular gingiva, 19 (∼14%) in the tongue, 15 (∼11%) in the buccal mucosa, 12 (∼8.5%) on the maxillary gingiva, 8 (∼5.7%) on the lower lip, 7 (∼5%) in the mandible, 4 (∼3%) in the retromolar mucosa, 3 (2%) in the upper lip, 2 (∼1%) in the floor of the mouth, and 2 (∼1%) in the maxilla. Among traumatic neuromas, 47 (∼63.5%) patients were females and 27 (∼36.5%) males. Age ranged from 5-90 years with a mean of 41 years. The location was known for 72 cases. Specifically, 23 (∼31%) were found in the tongue, 22 (∼30%) in the lower lip, 8 (∼11%) in the buccal mucosa, 6 (∼8%) in the palate, 3 (∼4%) in the mandibular gingiva, 3 (∼4%) in the upper lip, 2 (∼3%) in the maxillary gingiva and 1 (∼1%) on the floor of mouth. Among 48 schwannomas, 19 (∼39.6%) patients were females and 29 (∼60.4%) were males. Age ranged from 9-71 with a mean 31 years. The location was known for all cases. Specifically, 13 (∼27%) found in the tongue, 9 (∼19%) in the mandible, 5 (∼11%) in the mandibular gingiva, 5 (∼11%) in the lower lip, 4 (∼8%) in the upper lip, 4 (∼8%) in the palate, 4 (∼8%) in the buccal mucosa, 3 (∼6%) on the floor of mouth and 1(∼2%) in the maxillary gingiva. Among 39 PEN, 12 (∼30.7%) were females and 27 (∼69.2%) males. Age ranged from 20-71 year with a mean of 47 years. The location was known for 38 cases. Specifically, 22 (∼56%) found in the palate, 5 (∼13%) in the tongue, 4 (∼10%) in the maxillary gingiva, 4 (∼10%) in the upper lip, 2 (∼5%) in the lower lip and 1 (∼3%) in the maxilla. Of the two nerve sheath myxoma cases both patients were female. Also, among these peripheral nerve sheath tumors there were three hyperplastic neuromas that occurred in patients with MEN 2B. Histologically, most neurofibromas were solitary and showed typical histologic characteristics. Seven patients with solitary neurofibromas had neurofibromatosis type 1. Eleven neurofibromas were intraneural and 12 had a plexiform pattern with 3 of the 12 patients having a history of neurofibromatosis. Since plexiform neurofibromas are seen mostly in association with neurofibromatosis we tried to inquire additional patient information. Among schwannomas we identified 6 cases that were classified as plexiform. None of these patients had schwannomatosis. The above study represents the largest series of oral peripheral nerve sheath tumors.