Case Report Nerve Sheath Myxoma of the Gingiva: Report of a Rare Case and Review of the Literature Jose ´ D. Prado,* Rodrigo G. Andrade, † Yara T.C. Silva-Sousa, ‡ Marı ´lia F. Andrade,* Fernando A. Soares, † and Danyel E.C. Perez* ‡ Background: Nerve sheath myxoma (NSM) is an ex- tremely rare benign neoplasm in the oral cavity. This paper describes the first case, to our knowledge, of NSM in the gingival mucosa of an 84-year-old female patient. Methods: Intraoral examination revealed a painless and well-defined nodule in the lingual gingival mu- cosa of the right mandibular lateral incisor, which measured ;1.0 cm in diameter. The lesion was fully excised under local anesthesia, without intercurren- ces. Hematoxylin and eosin staining was performed in 5-mm sections for histopathologic analysis. Immu- nohistochemical reactions against vimentin and S-100 protein were carried out in 3-mm histologic sections in accordance with manufacturers’ instructions. Results: The patient’s medical history and an extrao- ral exam did not reveal other abnormalities. The patient wore a removable partial denture in the affected area. A trauma-induced gingival hyperplasia was the main di- agnostic hypothesis. Microscopically, the lesion was composed of an abundant myxoid matrix and stellated and spindle-shaped cells arranged in lobules separated by fine fibrous septa. The cells presented strong positiv- ity for vimentin and S-100 protein. According to the his- topathologic and immunohistochemical features, the diagnosis of NSM was established. After 9 months of treatment, no signs or symptoms of recurrences have been observed. Conclusion: Although NSM is an extremely rare oral tumor, it should be considered in the clinical differential diagnosis of gingival nodules. J Periodontol 2007; 78:1639-1643. KEY WORDS Gingiva; immunohistochemistry; nerve sheath myxoma; neurothekeoma; oral cavity. N erve sheath myxoma (NSM) is an uncom- mon benign peripheral nerve neoplasm that occurs most commonly in the skin of the head, neck, and trunk and is characterized by vari- able cellularity and abundant myxoid matrix. 1,2 NSM is known by several different terms, such as pacinian neurofibroma, bizarre cutaneous neurofibroma, cuta- neous lobular neuromyxoma, and perineural neuro- myxoma. 2 In 1969, Harkin and Reed 3 defined this tumor as nerve sheath myxoma, and later, Gallager and Helwing 4 used the term neurothekeoma. The most common gingival lesions are of reactive or inflammatory origin; the pyogenic granuloma, periph- eral giant cell lesion, and peripheral ossifying fibroma are the main lesions. 5-7 However, neoplastic lesions rarely occur in the gingiva, particularly lesions of the peripheral nerve. 8 To make a correct diagnosis of any gingival lesion, a detailed clinical exam and knowl- edge about the possible alterations that occur in this area are essential. In most cases, the definitive diagno- sis will be established through microscopic analysis of the specimen obtained by a surgical procedure. In the oral cavity, NSM is an extremely rare tumor, with only 22 previously published cases, in which none of the tumors affected the gingival mucosa. Thus, the aim of this paper is to report a case of oral NSM located in the gingiva and to review the literature. CASE REPORT In February 2006, an 84-year-old female patient was referred to the Department of Stomatology, A.C. Ca- margo Cancer Hospital, complaining of a painless oral nodule that she had for 2 years. A medical history and an extraoral exam did not contribute toward a diagnosis. The intraoral examination revealed a par- tially edentulous mandibular alveolar ridge, over which the patient used a removable partial denture. In the lingual gingival mucosa of the right mandibular lateral incisor, there was a painless and well-defined nodule, which measured ;1.0 cm in diameter and extended to an edentulous area where the partial prosthesis * Department of Stomatology, A.C. Camargo Cancer Hospital, Sa ˜o Paulo, SP, Brazil. † Department of Pathology, A.C. Camargo Cancer Hospital. ‡ Oral Pathology, University of Ribeira ˜o Preto, Ribeira ˜o Preto, SP, Brazil. doi: 10.1902/jop.2007.060425 J Periodontol • August 2007 1639