Hepatoid differentiation manifests as large polygonal cells with abundant clear and eosinophilic cytoplasm that are arranged in a trabecular, nested, or rosettoid pattern. The hepatoid nature of the clear tumor cells is demon- strated by bile production and immuno-phenotype [6]. Immunohistochemically, liver specific proteins, such as AFP and alpha-1 antitrypsin, are identified in the tumor cell. In the case presented here, the hepatoid area showed obvious positive immunoreactivity for AFP and alpha-1 antitrypsin, with negative glandular area. AFP is partic- ularly important for diagnosis because it is usually pos- itive in the tumors and elevated in the serum. However, HAC does not always produce AFP [3-5]. Although AFP positivity is important, it is not essential for a diagnosis of HAC. The diagnosis of HAC should be made on the basis of histopathological features of the tumor including im- munohistochemical analysis, because the behavior of Hepatoid adenocarcinoma of the gallbladder Fig. 3. (A) The gallbladder wall is replaced with infiltrating hepatoid adenocarcinoma composed of solid area, hepatoid carcinoma, with hyaline globules and conventional adeno- carcinomatous area (H&E, ×200). Immunohistochemical staining for alpha-fetoprotein (B) and alpha1-antitrypsin (C) was positive in the hepatoid area of the previously operated gallbladder specimen (×200). HAC is similar whether it produces AFP or not [3]. Hep Par1 has been used as a marker of hepatic differentiation, but subsequent studies have refuted its specificity and sensitivity [9,10]. In this case, Hep Par 1 was negative, and further studies are needed to determine its significance in diagnosis of HAC. The main differential diagnosis for HAC of the gall- bladder is HCC or combined HCC/cholangiocarcinoma invading the gallbladder. Van den Bos et al. [7] suggest the usefulness of magnetic resonance imaging as a prob- lem-solving tool for analysis of rare tumors of non-hep- atocellualr origin, including HAC of the gallbladder. In contrast to HCC or cholangiocarcinoma, HAC is charac- terized by high signal intensity in the periphery of the gall- bladder lesion on T2 weighted images and slow peripheral enhancement without capsule enhancement or washout. A review of previous reports [2-7] with HAC of the gall- thesurgery.or.kr 443