PATltOLOGY RESEARCH AND PRAcnCE o Urban & Fischer Verlag h ttp:/ /wNw. urbanf ischer. deljoumal stprp Tea<!hing Merkel Cell (Neuroendocrine) Carcinoma of the Vulva A Case Report with Immunohistochemical and Ultrastructural Findings and Review of the Literature Isabel Hierro, Alfredo Blanes, Alfredo Matilla, Santiago Munoz, Luis Vicioso and Francisco F. Nogales Departamento de Anatom ia Patol6gica, Facultad de Medicina, Universidad de Malaga and Servicio de Anatomfa Patol6gica, Hospital de Antequera, Ma l aga, Spain Summary A new case of primary Merkel cell carcinoma (MCC) of the vulva is reported and the literature reviewed for not- ing its clinical presentation, microscopic, immunohisto- chemical and ultrastructural features, as we ll as for es- tablishing the role of immunohistochemistry in the ulti- mate diagnosis of this uncommon and aggressive tumor. The lesion occun'ed in a 79 year o ld patient. His- tologically, the tumor was composed of intradermal small ce ll s with high mitotic index and frequent apopto- sis. The immunohistochemical study showed positivity for wide spectrum and low molecular weight cytoker- atins, epithelial membrane antigen, ncurofilamenls, neuron specific enolase and chromogranin A. Electron microscopy revealed intermediate filaments in a typical globular paranuclear arrangemen t. The coexpression of cytokeratins (including cytokerat in 20) and neurofila- mems, both in typical globular paranuclear arrange- ment, made possible the diagnosis of MCC, differenti- ating it from other malignant small cell tumors such as neuroendocrine metastatic carcinoma. Key words: Small ce ll tumor - Merkel ce ll carcinoma - Neuroendoerine carcinoma of the vulva - Intermedi- ate filaments - Cytokeratin 20 Introduction Merkel ce ll carcinoma (MCC) is an uncommon neu- roendocrine carcinoma of the sk in. It is usually found in Path ol. R es . Pract. 196: 503-509 (2000) the head and neck areas of elderly patients and, rarely, in the oral or genital mucosa /2- 6, 8, 12 , 1 3, 19,20, 23,25, 26/. Described by Toker in 1972 /24J as trabecular car- cinoma, it has subsequently received many designa- tions: "murky cell" carcinoma, endocrine carcinoma, neuroendocrine carcinoma and primary small cell carci- noma of the skin /17, 21]. The term Merkel cell carcino- ma has prevailed due to its ultrastructural and immuno- histochemical characterisation [22, 27}. Its origin from the Merkel cell (MC) was proposed in 1978 /22J , sup- poned by the ultrastructural similarities between the neoplastic cells and the Me. MCCs tend to have an ag- gressive clinical course, with frequent local recurrences and regional and distant metastases {I6, 20}. MCC in the vulva was first described by Tang et al. (23 J in 1982. Since then, eleven new caSes have been reponed [2, 3, 4, 5, 6, 8, 12, 1 3, 19 , 26}. We have re- viewed the li terature in order to document its clinical, microscopic, ultrastructural and immunohistochemical features, prove the utility of immunohistochemistry in the diagnosis. and comment on the current treatment modalities in this uncommon and aggressive vulvar tumor. Address for correspondence: Ora . Isahcl Hierro, Departa- mento de Anatornla Patol6gica. Facultad de Medicina, Uni- ver sidad de Malaga, Campus Uni v ersitario de Teatinos, sIn., 29078 1 Malaga. Spain. Tel.: ++34 95/213 1 520. Fax: ++34 95/213 1660 0344-033 812000/196n- 503 $ 12.0010