Cystadenoma with mesenchymal stroma (CMS) in the liver and bile ducts. A clinicopathologic study of 17 cases, 4 with malignant change

This study of 17 cases describes a homogeneous clinicopathologic group of tumors previously subsumed under the general term, hepatobiliary cystadenoma. This unique group of neoplasms that the authors have termed "cystadenoma with mesenchymal stroma" (CMS), occurred exclusively in women and showed two essential tumor components: a cyst lining of columnar to cuboidal, mucin secreting epithelium; and a moderately to densely cellular stroma composed of spindle (rarely oval) cells. The stromal element appeared similar to primitive mesenchyme, both on light and electron microscopic study, showing variable differentiation toward fibroblasts, smooth muscle, adipose tissue and capillaries. Cases of hepatobiliary "cystadenoma" in the literature with histology similar to CMS had similar sex and age incidences, while histologically dissimilar cases, lacking the mesenchymal stroma, had significantly different parameters. Four cases of CMS in this series showed malignant change that was manifested as papillary adenocarcinoma, suggesting the need for complete surgical removal of these premalignant neoplasms.