ORIGINAL ARTICLE PNL2 MELANOCYTIC MARKER IN IMMUNOHISTOCHEMICAL EVALUATION OF PRIMARY MUCOSAL MELANOMA OF THE HEAD AND NECK Luc G. Morris, MD, 1 Yong Hannah Wen, MD, PhD, 2 Daisuke Nonaka, MD, 2 Mark D. DeLacure, MD, 1 David I. Kutler, MD, 1 Youming Huan, MD, 3 Beverly Y. Wang, MD 2 1 Head and Neck Surgery Service, New York University Cancer Institute, New York, New York 2 Department of Pathology, New York University School of Medicine, New York, New York. E-mail: Beverly.Wang@nyumc.org 3 Department of Pathology, Mount Sinai School of Medicine, New York, New York Accepted 11 October 2007 Published online 28 January 2008 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/hed.20785 Abstract: Background. Histologic diagnosis of mucosal mel- anoma of the head and neck is difficult, requiring immunohisto- chemical stains which are less reliable than in cutaneous lesions. PNL-2 is a novel marker that has not been examined in mucosal melanoma. Methods. Nine formalin-fixed tissue sections of mucosal mela- noma were stained with PNL-2, human melanoma black (HMB)-45, Melan-A, S-100, and microphthalmia transcription factor (MITF). Results. Disease in all 9 patients arose from the sinonasal mucosa. Rates of diffuse positive staining with the 4 stains were PNL-2 (77.8%), HMB-45 (77.8%), Melan-A (50%), S-100 (87.5%), and MITF (40%). In 3 patients, PNL2 staining was superior to Melan-A or MITF. Conclusion. We report the first characterization of PNL-2 staining in head and neck mucosal melanoma. PNL-2 de- monstrates high sensitivity for mucosal melanoma, likely superior to Melan-A and MITF, and comparable to HMB-45, with specificity superior to S-100. We advocate inclusion of PNL2 as an important adjunctive marker in the evaluation of these lesions. V V C 2008 Wiley Periodicals, Inc. Head Neck 30: 771–775, 2008 Keywords: mucosal melanoma; melanoma; PNL2; immunohis- tochemistry; monoclonal antibody While malignant melanoma is a common skin neoplasm encountered in the head and neck, primary mucosal melanoma is rare, accounting for only 4% of melanomas in the head and neck. 1,2 Nevertheless, the head and neck—par- ticularly, the nasal cavity and sinonasal mu- cosa—constitutes the most common location of mucosal melanoma. 3,4 The appearance of these lesions is highly vari- able. Clinically, tumors may appear macular, ulcerated, or nodular, with colors ranging from melanotic to violaceous to pink to white. Histologi- cally, cells may be epithelioid, plasmacytoid, or spindled, arranged in sheet-like, alveolar, neuro- tropic, or desmoplastic configurations. Melanin pigment may be seen in 77% to 90% of lesions. 5 Occasionally, lesions are amelanotic. Unlike cutaneous melanoma, the highly vari- able gross and histologic appearance of mucosal melanoma often creates diagnostic difficulties dif- ferentiating between mucosal melanoma and other tumors, such as poorly differentiated carci- noma, lymphoma, plasmacytoma, rhabdomyosar- coma, esthesioneuroblastoma, and others. Correspondence to: B. Y. Wang The first two authors contributed equally to this work. V V C 2008 Wiley Periodicals, Inc. PNL2 Melanocytic Marker in Mucosal Melanoma HEAD & NECK—DOI 10.1002/hed June 2008 771