ORIGINAL ARTICLE Prognostic factors in Merkel cell carcinoma: Analysis of 240 cases Tina I. Tarantola, MD, a Laura A. Vallow, MD, d Michele Y. Halyard, MD, e Roger H. Weenig, MD, g Karen E. Warschaw, MD, f Travis E. Grotz, MD, b James W. Jakub, MD, b Randall K. Roenigk, MD, a Jerry D. Brewer, MD, a Amy L. Weaver, MS, c and Clark C. Otley, MD a Rochester and Minneapolis, Minnesota; Jacksonville, Florida; and Scottsdale, Arizona Background: Knowledge regarding behavior of and prognostic factors for Merkel cell carcinoma (MCC) is limited. Objective: We sought to further understand the characteristics, behavior, prognostic factors, and optimal treatment of MCC. Methods: A multicenter, retrospective, consecutive study of patients with known primary MCC was completed. Overall survival and survival free of locoregional recurrence were calculated and statistical analysis of characteristics and outcomes was performed. Results: Among the 240 patients, the mean age at diagnosis was 70.1 years, 168 (70.0%) were male, and the majority was Caucasian. The most common location was head and neck (111, 46.3%). Immunosup- pressed patients had significantly worse survival, with an overall 3-year survival of 43.4% compared with 68.1% in immunocompetent patients. In our study, patients with stage II disease had improved overall survival versus those with stage I disease, in a statistically significant manner. Patients with stage III disease had significantly worse survival compared with stage I and with stage II. Primary tumor size did not predict nodal involvement. Conclusion: The data presented represent one of the largest series of primary MCC in the literature and confirm that MCC of all sizes has metastatic potential, supporting sentinel lymph node biopsy for all primary MCC. Because of the unpredictable natural history of MCC, we recommend individualization of care based on the details of each patient’s tumor and clinical presentation. ( J Am Acad Dermatol 10.1016/ j.jaad.2012.09.036.) Key words: Merkel cell carcinoma; neuroendocrine carcinoma; nonmelanoma skin cancer; primary neuroendocrine carcinoma of skin; prognosis; retrospective. M erkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor most common on the head and neck of elderly Caucasian patients. Ultraviolet exposure and the Merkel cell polyomavirus appear pathogenic for MCC. 1 Histologically, MCC forms sheets and cords of small blue cells, typically in the dermis or subcu- taneous tissue. Immunostains used to distinguish these tumors include CK 20 or CAM5.2 in a perinu- clear dot pattern, and S-100, TTF-1, CK 7, and CD 45. No large-scale prospective studies have been com- pleted, and our understanding of MCC is based on retrospective reviews. Our objective was to collect all cases of MCC consulted on at a large, multicenter medical foundation and determine prognostic factors. From the Department of Dermatology, a Department of Gastro- enterologic and General Surgery, b and Division of Biomedical Statistics and Informatics, c Mayo Clinic, Rochester; Department of Radiation Oncology, Mayo Clinic, Jacksonville d ; Departments of Radiation Oncology e and Dermatology, f Mayo Clinic, Scotts- dale; and Department of Dermatology, University of Minnesota, Minneapolis. g Funding sources: None. Conflicts of interest: None declared. Previously presented orally in the Tromovitch Award finalist session at the Annual Meeting of the American College of Mohs Surgery, New York, NY, May 2, 2010. Accepted for publication September 14, 2012. Reprint requests: Tina I. Tarantola, MD, Skin Cancer Center of NW Florida, 540 Fontaine St, Pensacola, FL 32503. E-mail: tinatarantola@hotmail.com. Published online November 27, 2012. 0190-9622/$36.00 Ó 2012 by the American Academy of Dermatology, Inc. http://dx.doi.org/10.1016/j.jaad.2012.09.036 1