Mucinous cystic neoplasms (MCNs) are generally defined as cyst-forming epithelial neoplasms that arise in the pancreas and harbor characteristic ovarian-type stroma beneath the epithelium. In this study, we compared the immunoreactivity of steroid-related factors in these subepithelial stromal cells in MCNs to those in intraductal papillary mucinous neoplasms (IPMNs) to further characterize this unique MCN ovarian-type stroma through evaluation of sex steroid biosynthesis. Twenty MCNs and twenty IPMNs were examined. Immunoreactivity of steroid hormone receptors, including estrogen receptor (ERα and ERβ), progesterone receptor (PR, PR-A, and PR-B), and androgen receptor (AR), was more frequently detected in MCN ovarian-type stromal cells than in IPMN stromal cells (P< 0.01). The H-scores (mean ± SD) of steroidogenic factor (SF)-1 were also significantly higher in MCNs (112.3 ± 33.1) than in IPMNs (0.9 ± 1.2) (P< 0.01). The steroidogenic enzymes cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), cytochrome P450 17 alpha-hydroxylase (P450c17) and 3β-hydroxysteroid dehydrogenase (3β-HSD) showed immunoreactivity in 9/20 (45.0 %), 15/20 (75.0 %) and 13/20 (65.0 %), respectively, of ovarian-type stroma from MCN cases. These results demonstrate that the ovarian-type stroma of MCNs can express steroidogenic enzymes. Thus, the ovarian-type stroma of MCNs can produce sex steroids that may also act on these cells.