Mixed tumor, eccrine type, is a rare cutaneous adnexal neoplasm, mostly reported as isolated case reports. A systematic analysis of its histopathologic and immunohistochemical features has not previously been performed on a large series. The purpose of our investigation was to study a large number of cutaneous eccrine mixed tumors so as to fully characterize the entire spectrum of changes in the epithelial and stromal components, with an emphasis on unusual histopathologic features that may represent a diagnostic pitfall. This article reports a light microscopic and immunohistochemical study of 50 cases of eccrine mixed tumor, complemented by a literature review. Our study identified some unusual histopathologic features, thus extending the morphologic spectrum of this neoplasm. These included prominent cribriform areas, clear cell change, pseudorosette structures, prominent osseous metaplasia, and physaliphorous-like cells. Most of these features have not been previously recorded in eccrine mixed tumors and may represent a potential diagnostic pitfall.
From the *Sikl's Department of Pathology, Charles University Medical Faculty Hospital, Pilsen, Czech Republic; †Bioptical Laboratory, Pilsen, Czech Republic; ‡Dermatohistopathologische Gemeinschaftspraxis, Friedrichshafen, Germany; §Clinical Department of Dermatology and Venereology, Innsbruck Medical University, Innsbruck, Austria; ¶Department of Dermatology, Fundación Jiménez Díaz, Univesidad Autónoma, Madrid, Spain; ‖Division of Anatomical Pathology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa; **Department of Pathology, IRCCS-Ospedale “Casa Sollievo della Sofferenza,” San Giovanni Rotondo, Italy; ††Department of Dermatohistology, Catholic Clinics, Duisburg, Germany; and ‡‡Kempf und Pfaltz, Histologische Diagnostik, Zürich, Switzerland.
Reprints: Dmitry V. Kazakov, MD, PhD, Sikl's Department of Pathology, Charles University Medical Faculty Hospital, Alej Svobody 80, 304 60 Pilsen, Czech Republic (e-mail: firstname.lastname@example.org).