Merkel cell carcinoma is an aggressive neuroendocrine tumor historically thought to arise from neural crest-derived cutaneous neuroendocrine cells. Recent evidence supports an epidermal origin. We present a case of Merkel cell carcinoma arising on the upper arm of a 94-year-old woman that had multiple morphologic patterns: small cells typical of Merkel cell carcinoma, malignant cells with squamous differentiation and malignant poorly differentiated spindle cells. Subsequent metastatic disease in regional lymph nodes showed only the small cells and the malignant spindle cells. To our knowledge, this is the first case of Merkel cell carcinoma showing these three patterns of differentiation at first presentation. This morphology raises the possibility that Merkel cell carcinomas may arise from epidermal stem cells that can differentiate along different lines.

Imaging features of benign mixed Brenner tumor and mucinous cystadenomas are rarely reported. This report aims to describe the case of a benign mixed Brenner tumor and mucinous cystadenoma with a dominant Brenner tumor component and to review the typical imaging features of this ovarian neoplasm.