A case of a CA 19-9 producing cystadenoma with mesenchymal stroma originating from the common hepatic duct is presented, with a review of the literature. The findings of ultrasound and CT scans and the endoscopic retrograde cholangiopancreatography picture allowed the establishment of a confident pre-operative diagnosis. Although there was an elevation of CA 19-9 serum levels, the resected specimen did not show any malignant focus at pathologic examination. After surgical excision, CA 19-9 serum levels returned to normal.