Hepatoid adenocarcinoma - review of the literature illustrated by a rare case originating in the peritoneal cavity.

Hepatoid adenocarcinoma (HAC) is a rare and aggressive extrahepatic tumour, morphologically mimicking hepatocellular carcinoma (HCC). However, immunophenotype and location are heterogeneous. We report the case of a 21-year-old man with HAC of the peritoneal cavity and summarize data from the 261 HAC cases published so far. The most common HAC locations were stomach (63%), ovaries (10%), lung (5%), gallbladder (4%), pancreas (4%), and uterus (4%). With the exception of gallbladder HAC, there was a male predominance (M:F = 2.4:1). Median age was 65 years (range 21-88). Fatigue, weight loss, abdominal masses, and pain were common findings. One-year survival was 55% and median overall survival 11 months (range 0.1-102). The outstanding diagnostic feature of HAC is positivity for alphafetoprotein (AFP) (88%), HepPar1 (63%), and EpCAM antibodies HEA125 or MOC31 which show no reactivity with hepatocytes. Due to the beneficial effect of sorafenib in HCC and strong activation of EGFR, ERK1 and AKT1, our patient received sorafenib. Despite temporary clinical improvement, he died 6 months after the diagnosis. The diagnostic panel of HAC should include AFP, HepPar1, and EpCAM antibodies. EpCAM reactivity excludes HCC. HAC has a poor prognosis.