The literature is highly conflicting on hepatobiliary mucinous cystic neoplasms (MCNs), aka "hepatobiliary cystadenoma/cystadenocarcinoma," largely because ovarian stroma (OS) was not a requirement until WHO-2010 and is not widely applied even today. In this study, MCNs (with OS) accounted for 24 of 229 (11%) resected hepatic cysts in one institution. Eight of the 32 (25%) cysts that had been originally designated as hepatobiliary cystadenoma/cystadenocarcinoma at the time of diagnosis proved not to have an OS during this review and were thus re-classified as non-MCN. In total, 36 MCNs (with OS) were analyzed-24 from the institutional files and 12 consultation cases. All were women. Mean age was 51 (28 to 76 y). Mean size was 11 cm (5 to 23 cm). Most (91%) were intrahepatic and in the left lobe (72%). Preoperative imaging mentioned "neoplasm" in 14 (47%) and carcinoma was a differential in 6 (19%) but only 2 proved to have carcinoma. Microscopically, only 47% demonstrated diffuse OS (>75% of the cyst wall/lining); OS was often focal. The cyst lining was often composed of non-mucinous biliary epithelium, and this was predominant in 50% of the cases. Degenerative changes of variable amount were seen in most cases. In situ and invasive carcinoma was seen in only 2 cases (6%), both with small invasion (7 and 8 mm). Five cases had persistence/recurrence, 2 confirmed operatively (at 7 mo and 15 y). Of the 2 cases with carcinoma, one had "residual cyst or hematoma" by radiology at 4 months, and the other was without disease at 3 years. In conclusion, many cysts (25%) previously reported as hepatobiliary cystadenoma/cystadenocarcinoma are not MCNs. True MCNs are uncommon among resected hepatic cysts (11%), occur exclusively in females, are large, mostly intrahepatic and in the left lobe (72%). Invasive carcinomas are small and uncommon (6%) compared with their pancreatic counterpart (16%). Recurrences are not uncommon following incomplete excision.