There are several recent reports describing hybrid peripheral nerve sheath tumors showing a biphasic component of neoplastic cells. These combinations include a mixture of neurofibroma and schwannoma, schwannoma and perineurioma, neurofibroma and perineurioma, and perineurioma and granular cell tumor. A case of a triphasic combination of neurofibroma, schwannoma, and perineurioma has also been described. We describe the clinicopathologic and immunohistochemical characteristics of 9 cases of a benign cutaneous plexiform nerve sheath tumor located on the lips and exhibiting hybrid features of perineurioma and cellular neurothekeoma. Clinically, lesions were solitary dome-shaped papules located on the lips. Histopathologically, the neoplasms consisted of well-circumscribed but uncapsulated dermal nodules with a plexiform pattern. They were composed of nests or rounded aggregations of neoplastic cells embedded in a slightly myxoid stroma. Within the aggregates, cells were distributed in a storiform and lamellar pattern. Immunohistochemically, most neoplastic cells expressed strong immunoreactivity for S100A6, MiTF, NKI/C3, PGP9.5, EMA, and NSE, whereas variable, focal, and weaker positivity for CD34, claudin-1, and Glut-1 was seen in some cases. On the basis of these findings, we believe that this neoplasm is a distinctive benign cutaneous plexiform nerve sheath tumor with histopathologic and immunohistochemical hybrid features of perineurioma and cellular neurothekeoma.
*Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain
†Department of Pathology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
‡Department of Dermatology, Research Unit Dermatopathology, Medical University of Graz, Austria
§Dermatopathology Laboratory, Darmstadt
∥Dermatophatologische Gemeinschaftslabor, Friedrichshafen, Germany
¶Departments of Pathology and Dermatology, University of California, San Francisco, CA
Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Correspondence: Luis Requena, MD, Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Avd. Reyes Católicos 2, 28040-Madrid, Spain (e-mail: firstname.lastname@example.org).