Intraoral sclerosing perineurioma: a case report and review of the literature Wilfredo Alejandro González-Arriagada, DDS, MSc, a,b Jorge Esquiche Leon, DDS, PhD, a Pablo Agustin Vargas, DDS, PhD, a Oslei Paes de Almeida, DDS, PhD, a and Marcio Ajudarte Lopes, DDS, PhD, a Piracicaba, Brazil ORAL DIAGNOSIS DEPARTMENT, SEMIOLOGY, AND ORAL PATHOLOGY, PIRACICABA DENTAL SCHOOL, STATE UNIVERSITY OF CAMPINAS Sclerosing perineurioma is an extraneural soft tissue lesion that has been reported in the extremities of young adults. It is composed of oval epithelioid or plump spindled cells scattered to form ill-defined fascicles in a storiform, whorled, or trabecular pattern and dermal sclerosis represented by thickened collagen bundles in a lamellar array that express epithelial membrane antigen and are negative for S-100 protein. The treatment is surgical excision, and no recurrence or metastases are expected. Herein is presented the first case of intraoral sclerosing perineurioma of the lower lip, emphasizing its histopathologic and immunohistochemical features. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:e46-e52) The perineurioma is an unusual benign soft tissue tu- mor composed of cells derived from the perineurium. Two forms of perineurioma are described: intraneural perineurioma and soft tissue perineurioma (extraneu- ral). 1-3 Sclerosing perineurioma (SP) is considered to be a variant of the soft tissue perineurioma and was first described in 1997 by Fetsch and Miettinen 2 in a clini- copathologic study of 19 cases, which showed a predi- lection for the fingers and palms of young male adults. Since then, only 22 additional cases have been reported, almost all affecting the hands. 3-15 The differential di- agnosis includes fibroma of the tendon sheath, fibrosing tenosynovial giant cell tumor and Morton neuroma. SP occurs mainly in men and in the third decade of life. The most common clinical presentation is a painless solitary small lesion with a long history of evolution affecting the extremities, particularly the fingers. 2 Microscopically, it is a well circumscribed and hy- pocellular tumor surrounded by a thin fibrous pseudo- capsule which is composed of oval epithelioid or plump spindled cells forming ill-defined fascicles in a storiform, whorled, or trabecular pattern and der- mal sclerosis represented by thickened collagen bun- dles in a lamellar array. 3-5 Immunohistochemical studies have showed positivity for EMA, CD99, vi- mentin, and collagen type IV, but negativity for S-100, MART-1, factor XIIIa, CD34, muscle-spe- cific actin, alpha smooth muscle actin, desmin, Ki- 67, cytokeratin, and p53. 3-6,8 The treatment consists of complete local excision, and recurrence or metastases are not reported so far. 2-6,11,12 SP is extremely rare, and to the best of our knowledge this is the first reported case affecting the oral cavity. CASE REPORT A 26-year-old man was referred complaining of a painless nodule in the lower lip mucosa. The patient related that the lesion had been present for 10 years, with very slow growth in the first years and then remaining stable, without causing any inconvenience during chewing or speaking. Oral exami- nation revealed a poorly circumscribed, soft, sessile nodule with a smooth and normal-colored surface, 2.0  2.0 cm in its maximum dimensions (Fig. 1). The patient did not show signs of sensorial alteration in the affected region, and he did not remember previous local trauma. With the clinical diagnosis of mucocele or a benign mesenchymal tumor, an excisional biopsy was performed. Histopathologic analysis revealed, at low-power magnifica- tion, a sclerotic stroma with some cellular nests (Fig. 2, A), accompanied by nervous fascicles or twigs with evident per- ineurium at the periphery with a thin capsule (Fig. 2, B). The lesion showed the presence of abundant vascularization with perivascular distribution of neoplastic epithelioid cells and 2 different areas: a sclerotic fibrous-hypocellular area; and per- ineurial cells associated with inflammatory infiltrate (Fig. 2, C). At higher magnification, the histologic features included infiltration of muscular tissue by neoplastic cells and sclerotic tissue. The tumor cells were isolated or were organized in cellular nests, which were arranged in whorled growth patterns, similar to onion skins, and intermixed with collagen bundles. Also, the neoplastic cells were small spindled-shaped or epithe- a Oral Diagnosis Department, Semiology and Oral Pathology, Piraci- caba Dental School, State University of Campinas (UNICAMP), Piracicaba, Sao Paulo, Brazil. b Oral Pathology and Diagnosis, Dental School, University of Val- paraíso, Valparaíso, Chile. Received for publication Nov 19, 2009; returned for revision Jan 13, 2010; accepted for publication Jan 26, 2010. 1079-2104/$ - see front matter © 2010 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2010.01.021 e46