Abstract
A 78 year old Caucasian woman, was admitted to the hospital for evaluation of a mass to the anterior surface of the left mandibular angle and left submandibular area present for the past year with rapid acceleration of growth over three weeks prior to admission. An incisional biopsy was performed and initial diagnosis of poorly differentiated neuroendocrine carcinoma (small cell carcinoma) was made. Dermatological evaluation revealed lesion was suspicious for Merkel cell carcinoma and the pathology specimen was re-analyzed and differential diagnoses was made for Merkel cell carcinoma. Patient was educated and discharged to a nursing home with plan for irradiation, chemotherapy, and outpatient follow up. This case study serves to raise awareness of a rare condition and describe how Merkel cell carcinoma may be mistaken for similarly presenting neuroendocrine tumors.
Highlights
Merkel cell carcinoma (MCC) is a rare and highly aggressive neuroendocrine carcinoma with etiology related to the Merkel-Ranvier tactile epithelial cells necessary for light touch
Majority of all the reported cases of Merkel cell carcinomas are caused by Merkel Cell Polyomavirus (MCPyV), which incorporates itself into the genome of cancerous Merkel cells leading to a monoclonal proliferation—a pattern indicating the virus initially integrated into a single cell [1]
Who found via inactivation of protein expression in MCPyV infected Merkel cells that protein expression was necessary in order to “maintain the tumor phenotype—the so-called oncogene addiction” [3]
Summary
Merkel cell carcinoma (MCC) is a rare and highly aggressive neuroendocrine carcinoma with etiology related to the Merkel-Ranvier tactile epithelial cells necessary for light touch. Majority of all the reported cases of Merkel cell carcinomas are caused by Merkel Cell Polyomavirus (MCPyV), which incorporates itself into the genome of cancerous Merkel cells leading to a monoclonal proliferation—a pattern indicating the virus initially integrated into a single cell [1]. Shuda et al, in 2008 demonstrated MCPyV infected Merkel cells may contain specific T-antigen specific mutations rendering them susceptible to MCPyV infection and progression to carcinoma [2]. The cases not attributable to MCPyV have an unknown etiology [4], but evidence exists for UV associated mutations “underlying the etiology of MCPyV-negative Merkel cell carcinomas” [5]. Merkel Cell carcinomas commonly occur on sun exposed areas such as the head, neck, extremities, and major risk factors include UV light exposure, advanced age, and immunosuppressed states [7]. “Immunodeficiency conditions are related both to polyomavirus-associated and to UV-associated MCC, suggesting that immune system’s alteration plays a role in the pathogenesis of both types of MCC” [8]
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