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.