Perforated gastric metastasis of Merkel cell carcinoma: Case report and review of the literature

Abstract

A 53 year-old Vietnamese male presented with a complaint of a left buttock mass which had grown to 8.0 cm during the past three years. A CT scan revealed the gluteal lesion and a large mass of the stomach. A biopsy of the gluteal skin lesion was diagnosed as a high grade neuroendocrine carcinoma consistent with Merkel cell carcinoma. Tumor cells in the gastric biopsy showed the same morphology and immunophenotype as seen in the skin biopsy, and expressed synaptophysin, chromogranin, CD56, and cytokeratin (CK) 20 with perinuclear dot-like staining. The diagnosis of gastric metastasis of Merkel cell carcinoma was further confirmed by immunohistochemistry for Merkel cell polyomavirus (MCPyV). The patient underwent one cycle of chemotherapy until he presented with a perforation of the gastric lesion. Surgical resection was performed, with subsequent pathologic analysis of the stomach lesion interpreted as metastatic Merkel cell carcinoma. Herein we describe the first case of perforated gastric metastasis of Merkel cell carcinoma. Histopathological diagnosis of perforated gastric metastasis of Merkel cell carcinoma was established by characteristic immunostains for CK20 and MCPyV in addition to the positive stains for neuroendocrine markers (synaptophysin, chromogranin and CD56). Keywords: Merkel cell carcinoma, Gastric metastasis, Perforation, Merkel cell polyomavirus, Immunohistochemistry