Research ArticlesCyclooxygenase-2 Expression in Primary and Metastatic Merkel Cell CarcinomaJoachims, Zohar MD*; Feinmesser, Raphael MD*; Purim, Ofer MD†; Halpern, Marisa MD‡; Brenner, Baruch MD†; Fenig, Eyal MD†; Roizman, Pepi MSc*; Sulkes, Jaqueline PhD§; Feinmesser, Meora MD‡Author Information Departments of *Otolaryngology ‡Pathology §Unit of Epidemiology †Institute of Oncology, Rabin Medical Center, Beilinson Hospital, Petah Tiqwa and Felsenstein Medical Research Center, both associated with Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel Reprints: Meora Feinmesser, MD, Department of Pathology, Rabin Medical Center, Beilinson Campus, Petah Tiqwa 49100, Israel (e-mail: [email protected]). Received for publication August 18, 2007; accepted October 24, 2007 Applied Immunohistochemistry & Molecular Morphology: October 2008 - Volume 16 - Issue 5 - p 442-446 doi: 10.1097/PAI.0b013e31815f982a Buy Metrics Abstract Cyclooxygenase-2 (COX-2) is involved in the development and progression of many tumors, and its inhibition has been shown to block tumor growth. This study examined COX-2 expression in primary and metastatic Merkel cell carcinoma (MCC). Formalin-fixed paraffin-embedded tissues from 26 primary MCCs and 7 lymph node metastases were stained immunohistochemically with a monoclonal antibody directed against COX-2, and the percentage and intensity of staining were analyzed semiquantitatively. Immunopositivity for COX-2 was found in 20 primary tumors (77%), and was diffuse in 16 of them (80%). Staining intensity was strong in 5 tumors (19%), moderate in 6 (23%), and weak in 9 (35%). Five metastases (71%) showed similar staining. Prominent mitotic activity was associated with more diffuse COX-2 immunopositivity. No association was found between COX-2 expression and outcome. This study confirms that most MCCs express COX-2 and shows that COX-2 expression is related to one parameter of aggressive behavior—a high mitotic rate—but not to any others. The possibility of treating MCC with COX-2 inhibitors should be considered. © 2008 Lippincott Williams & Wilkins, Inc.