Clinical Diagnosis
Merkel cell carcinoma presents a diagnostic challenge, as it is a relatively asymptomatic tumor with no pathognomonic features. Given the propensity for locoregional and distant metastasis, and the associated morbidity and mortality, early detection is im
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Clinical Diagnosis Nancy Kim, Sandra Y. Han, and Siegrid S. Yu
Introduction and History MCC was first described by Cyril Toker in 1972. He named it trabecular carcinoma of the skin because of its histological appearance of trabecular or column-like growth [1]. Toker initially believed MCC to be a tumor of sweat gland origin. In 1978, Tang and Toker performed ultrastructural studies of MCC which showed dense core neurosecretory granules in the cytoplasm of tumor cells [2]. As Merkel cells were known to be the only cells in the skin containing these granules, they hypothesized that trabecular carcinoma of the skin originated from Merkel cells [3, 4]. This continues to be debated in the literature with most current authors believing that MCC is related to Merkel cells and that the cells are of neuroendocrine origin [4, 5]. Other authors postulate that a pluripotent stem cell is responsible for MCC [6, 7].
N. Kim • S.S. Yu (*) Department of Dermatology, UCSF Dermatologic Surgery & Laser Center, 1701 Divisadero Street, Third Floor, San Francisco, CA 94115-0316, USA e-mail: [email protected]; [email protected]; [email protected] S.Y. Han Department of Dermatology, University of California, San Francisco, 1701 Divisadero Street, Third Floor, San Francisco, CA 94115, USA e-mail: [email protected]
With all the different hypotheses about the origin of MCC, it is not surprising that there have been a plethora of different names used to describe it in the literature such as trabecular carcinoma of the skin, cutaneous apudoma, primary small cell carcinoma of the skin, primary undifferentiated carcinoma of the skin, anaplastic carcinoma of the skin, cutaneous neuroendocrine carcinoma, and MCC [8]. The term Merkel cell carcinoma was first introduced in 1980 and has since become the most commonly used term to describe the tumor [9]. Merkel cell carcinoma is so rare that it was previously difficult to assess the true incidence of this disease. More recently, epidemiologic information has been gleaned through mining large cancer registries, which pool data across large regions. Agnelli and Clegg analyzed the population covered by the Surveillance Epidemiology and End Results (SEER) program of the National Cancer Institute [10, 11]. The year 1986 was chosen as the starting year for analysis because this was the inaugural year for the histologic code for MCC with the advent of the International Statistical Classification of Diseases and Related Health Problems (ICD) in the form of ICD-0, rendering it more easily trackable. Through this research it has become apparent that although rare, incidence of Merkel cell carcinoma is increasing. Reported incidence in the Surveillance, Epidemiology, and End Results (SEER) database has quadrupled from 1986 to 2006 likely because of new pathologic techniques that reduce the
M. Alam et al. (eds.), Merkel Cell Carcinoma, DOI 10.1007/978-1-4614-6608-6_3, © Springer Science+Business Media New York 2013
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number of missed diagnoses. In 1986 the incidence of Merkel cell carcinoma in the U
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