Merkel cell carcinoma: case report

Abstract

Abstract: 

Introduction: Merkel Cell Carcinoma (MCC) is a neuroendocrine neoplasm first described by Toker in 1972. Pathogenesis is not clear; but ultraviolet radiation, immunosuppression, and the presence of polymavirus (MCPyV) in the tumor genome seems to influence its development, it usually occurs in people over 60 years of age, preferably in the extremities and head and neck area. Clinically it looks like a single protruding lump with a hard consistency, very similar to other skin tumors. It is often accompanied by regional lymphadenopathy. Overall survival of stage I patients is 80%. On the contrary once distant metastases have developed, it is only of five months.

The objective of this presentation is to report a rare case of skin neoplasia with a very poor prognosis, its diagnostic approach, differential diagnoses and its viral etiology.

Presentation of the case: 55-year-old woman who consults for a tumor lesion in her elbow. Biopsy was decided: a 6 x 5cm skin lozenge that, on the surface, presented a raised, brown and ulcerated tumor lesion. When cut it had a whitish gray color, firm consistency and a maximum thickness of 4,5 cm. Sample was processed with the usual technique for staining with hematoxylin/eosin. Histologically, a proliferation of invasive neoplasic cells of neuroendocrine lineage was observed, arranged in large nests separated by desmoplasic stroma. It presented small, round and blue cells, with little and poorly defined cytoplasm and nuclei with finely granular “salt and pepper” chromatin. Mitosis count was high and extensive areas of necrosis were observed. The tumor compromised the entire thickness of the sample, contacting the surgical margin. This study is complemented with immunohistochemistry: CK 20 +, AE1/AE3 +, synaptophysin +, INSIM.1 +, polyoma virus +.

Conclusion: the MCC constitutes the skin neoplasm with the worst prognosis. Our case was related to viral etiology confirmed by immunohistochemistry. It is necessary to distinguish it from cutaneous lymphomas, which have a better prognosis. Therefore, its rapid diagnosis with immunohistochemical confirmation is essential for timely treatment.