Merkel cell carcinoma in the left groin: A case report and review of the literature

Abstract

Merkel cell carcinoma (MCC) is a relatively rare but aggressive primary neuroendocrine carcinoma of the skin. MCC frequently occurs on sun-exposed areas in elderly Caucasian patients and has a propensity for local recurrence, regional lymph node invasion and distant metastases. However, MCC occurring on sites that are not sun-exposed in Asian patients is extremely uncommon. The current study describes the case of a 66-year-old Chinese male who presented with an asymptomatic, smooth lesion in the left inguinal region, which was initially diagnosed as a malignant lymphoma. Upon histological and immunohistochemical analysis, the tumor was consistent with the diagnosis of an MCC. In conclusion, due to its low incidence rate and lack of characteristic clinical manifestations, the final diagnosis of MCC relies on the analysis of histological findings and immunohistochemical markers following lesion biopsy or resection. The present study aimed to report a case of MCC and present a brief literature review in order to bring attention to the diagnosis of this condition.

Keywords: Merkel cell carcinoma; differential diagnosis; histopathology; immunohistochemistry; neuroendocrine carcinoma.

Figure 1

(A) Sheets of round to oval, small, blue cells with amphophilic sparse cytoplasm and vesicular nuclei [hematoxylin and eosin (HE); magnification, ×400). (B) Diffuse distribution of neoplastic cells and deep mesenchyme infiltration (HE; magnification, ×100). (C) Vascular proliferation in interstitial substance with staining for cluster of differentiation 34 (magnification, ×100). (D) Merkel cell carcinoma (MCC) with diffusely-positive staining for synaptophysin (magnification, ×400). (E) MCC with diffusely-positive staining for chromogranin (magnification, ×400). (F) Positive staining for cytokeratin (CK)20, with a perinuclear dot-like pattern, supporting the diagnosis of MCC (magnification, ×400). (G) Positive staining for CK8/18, with a perinuclear dot-like pattern (magnification, ×400). (H) MCC with diffusely-positive staining for epithelial membrane antigen (magnification, ×400).