CLINICAL PATHOLOGIC CHALLENGE ANSWER Asymptomatic Soft Erythematous Dome-Shaped Papule on the Chest: Answer Amira Elbendary, MBBCh, MSc,*† Manuel Valdebran, MD,* Sarah Velasquez, MD,* Jonathan Truong, HTL, QIHC, BS,* Douglas J. Pravda, DO,‡ and Elen Blochin, MD, PhD* (Am J Dermatopathol 2017;39:867–869) (Continued from page e155) ANSWER Benign epithelioid schwannoma. Further immunohistochemical studies revealed strong positivity for S100, NKI/C3, and vimentin. Some cells were positive for SOX 10. Importantly, collagen type IV was seen in a diffuse pericellular distribution and around small groups of cells (Fig. 1). Staining with EMA, HMB45, CD68, pan- keratin, EMA, and GFAP demonstrated negative results. MIB-1 highlighted a low proliferative fraction (Fig. 2). The diagnosis of an epithelioid schwannoma was rendered. Benign peripheral nerve sheath tumors are common mesenchymal neoplasms. Epithelioid schwannoma (ES) is a rare and diagnostically challenging variant of schwannoma that was first described in 1993. 1 Less than 60 cases have been reported to date in the literature. 2–5 ES is a rare variant of schwannoma, commonly affecting the head and neck regions followed by extremities and trunk. Wide age distribution has been reported (17–73 years) with slight female predominance. 2,4 Most commonly, ES is present as asymptomatic slow growing mass or nodule, although painful lesions and lesions associated with periph- eral neuropathy have been reported. 6 Usually they are described as single lesions. Multiple lesions have been re- ported in the context of Carney syndrome. 5 Microscopically, epithelioid schwannoma demonstrates a single round to oval nodule or a multilobular growth pattern with moderate to high cellularity composed mainly of monomorphous epithelioid cells that form nests or loosely aggregated clusters, resembling multinucleation. 4 Peripher- ally, nerve twigs in adjacent nerve segments or in the capsule of the tumor could be noted. 4 In contrast to the conventional type of schwannoma, ES may not possess a capsule, the characteristic alternation of Antony A and Antony B areas or Verocay bodies. The epithelioid cells contain small round to oval nuclei, less commonly reniform nuclei, with single nucleoli and intranuclear pseudoinclusions. Mild nuclear aty- pia and low mitotic rate can be present. The tumor cells are positive for S100 protein, vimentin, collagen type IV, nerve growth factor receptor (NGFR), CD57, 3–5 while negative for HMB45, melan-A, CD34, kera- tin, CD68, epithelial membrane antigen (EMA), neurofila- ment protein, CD56, neural type cadherin, smooth muscle actin, and desmin. 3–5 ES is associated with a low recurrence rate on complete excision. No cases of metastasis have been reported in the literature. It is important to be aware of this unusual variant of schwannoma. The differential diagnosis of ES is summarized in Table 1. REFERENCES 1. Orosz Z, Sápi Z, Szentirmay Z. Unusual benign neurogenic soft tissue tumour. Epithelioid schwannoma or an ossifying fibromyxoid tumour? Pathol Res Pract. 1993;189:601–605. 2. Kindblom LG, Meis-Kindblom JM, Havel G, et al. Benign epithelioid schwannoma. Am J Surg Pathol. 1998;22:762–770. 3. Saad AG, Mutema GK, Mutasim DF. Benign cutaneous epithelioid Schwannoma: case report and review of the literature. Am J Dermatopa- thol. 2005;27:45–47. 4. Laskin WB, Fetsch JF, Lasota J, et al. Benign epithelioid peripheral nerve sheath tumors of the soft tissues: clinicopathologic spectrum of 33 cases. Am J Surg Pathol. 2005;29:39–51. 5. Smith K, Mezebish D, Williams JP, et al. Cutaneous epithelioid schwan- nomas: a rare variant of a benign peripheral nerve sheath tumor. J Cutan Pathol. 1999;26:213–214. 6. Ciau N, Eisele DW, van Zante A. Epithelioid schwannoma of the facial nerve masquerading as pleomorphic adenoma: a case report. Diagn Cy- topathol. 2014;42:58–62. 7. Laskin WB, Fetsch JF, Miettinen M. The “neurothekeoma”: immunohis- tochemical analysis distinguishes the true nerve sheath myxoma from its mimics. Hum Pathol. 2000;31:1230–1241. 8. Jo VY, Fletcher CD. Epithelioid malignant peripheral nerve sheath tumor: clinicopathologic analysis of 63 cases. Am J Surg Pathol. 2015; 39:673–682. 9. Michal M, Miettinen M. Myoepitheliomas of the skin and soft tissues: report of 12 cases. Virchows Arch. 1999;434:393–400. 10. Heffernan MP, Smoller BR, Kohler S. Cutaneous epithelioid angioleio- myoma. Am J Dermatopathol. 1998;20:213–217. From the *Ackerman Academy of Dermatopathology, New York, NY; †Department of Dermatology, Kasr Alainy Faculty of Medicine, Cairo University, Cairo, Egypt; and ‡Over Look Medical Center, Summit, NJ. The authors declare no conflicts of interest. Reprints: Elen Blochin, MD, PhD, Ackerman Academy of Dermatopathol- ogy, 145 E 32nd Street, New York, NY 10016 (e-mail: blokhinb@ yahoo.com). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Am J Dermatopathol  Volume 39, Number 11, November 2017 www.amjdermatopathology.com | 867 Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.