Microscopic description and IHC:

The cyst is multiloculated and does not communicate with any other structures.

Microscopically, the cyst is lined by columnar cells with low-grade dysplasia overlying ovarian type stroma (ER+)

The background liver shows features suggestive of mildly active steatohepatitis.

Discussion:

Mucinous cystic neoplasms arising in the liver are similar to their pancreatic counterparts. They usually occur in females and are composed of a mucin-producing columnar epithelial lining overlying an ovarian type stroma (the latter can be highlighted with CD10, inhibin, ER, or PR). In a large case series report by Regev et al, the authors presented 78 cases of cystic liver lesions greater than 4 cm from a large tertiary care medical center: The majority were simple cysts, echinococcal cysts=8, mucinous cystic neoplasms=8, invasive cystadenocarcinoma=1, and unclassifiable=4.

This report highlights importance of through sampling for cystic lesions in the liver to rule out higher grade component. For this particular case, 1 section per cm was submitted from random regions of the cyst.

References:

Regev, Arie, et al. "Large cystic lesions of the liver in adults: a 15-year experience in a tertiary center." Journal of the American College of Surgeons193.1 (2001): 36-45.

World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Digestive System, Aaltonen LA, Hamilton SR (Eds), IARC Press, Lyon, France 2000.

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