An alpha-fetoprotein-negative hepatoid adenocarcinoma of the gallbladder with squamous differentiation

Hepatoid tumors of the gastrointestinal/pancreatobiliary district: morphology, immunohistochemistry, and molecular profiles

Hepatoid tumors (HTs) histologically resemble hepatocellular carcinoma (HCC) but manifest outside the liver. Regarding immunohistochemistry (IHC), the classical markers of hepatoid differentiation are Hep Par-1, CD10, and arginase-1. This study provides a critical overview of HT in the gastrointestinal/biliopancreatic system, which is the most common site of origin. Gastric HTs are malignant neoplasms recognized by the current WHO classification as a variant of adenocarcinoma. In addition to the classic IHC markers, SALL4 and claudin-6 can help exclude a metastatic HCC at this site. Next-generation sequencing revealed the most common alterations, including TP53 mutation, microsatellite instability (MSI), and Her2 amplification. Esophageal HTs are exceptionally rare and usually arise in the context of Barrett's esophagus. In the intestine, HTs are classified within the adenocarcinoma spectrum and manifest more often in the background of inflammatory bowel disease. Regarding their molecular profile, recurrent alterations included MSI and NCOA4-RET fusions. In the pancreas, the current WHO classification acknowledges HT only as a possible variant of ductal adenocarcinoma, characterized by a poor prognosis. However, at this site, neuroendocrine tumors (NETs) and solid pseudopapillary neoplasms (SPNs) may also show hepatoid differentiation. Hepatoid NETs show aggressive behavior, whereas hepatoid SPNs harbor CTNNB1 mutations and are characterized by an indolent clinical course. Lastly, biliary HTs belong to the adenocarcinoma category and usually show a poor prognosis. In conclusion, gastrointestinal/pancreatobiliary HTs show specific histomolecular features, which should be considered for improving routine diagnostic activity and clinical management.

Approach to the Diagnosis of Hepatoid Adenocarcinoma, an Under-reported Entity: Case Series and Review of Literature

Hepatoid adenocarcinoma is a rare type of extra-hepatic adenocarcinoma which exhibits morphological, functional, and immunohistochemical features of hepatocellular carcinoma, hence correct diagnosis poses a challenge. The most frequent site of this tumor is stomach and rarely occurs in ovaries, lung, gallbladder, pancreas, uterus, and other sites. We present four cases of hepatoid adenocarcinoma of our hospital at rare sites like lungs and gallbladder along with literature review and a simplified approach to diagnosis. In absence of adequate immunohistochemistry or radiological findings often this entity is missed or misdiagnosed as metastatic hepatocellular carcinoma. We have analyzed these hepatoid adenocarcinoma cases in terms of various clinical, serological, histo-morphological, and immunohistochemical parameters, and propose a systematic approach to correctly diagnose this entity.

Primary Hepatoid Adenocarcinoma of Gallbladder With MB21D2/GALNT12/ARID2 Mutations: A Case Report

BACKGROUND

Primary hepatoid adenocarcinoma of the gallbladder is a relatively rare type of extrahepatic adenocarcinoma. The genetic changes involved in this type of adenocarcinoma were unexplained so far. We reported a rare case of primary hepatoid adenocarcinoma of gallbladder with Mab-21 domain containing 2 (MB21D2), polypeptide N-acetylgalactosaminyltransferase 12 (GALNT12), and AT-rich interaction domain 2 (ARID2) mutations, which was confirmed after surgical resection pathologically.

CASE SUMMARY

A 69-year-old female with distention of hypogastrium and constipation received enema treatment, but ineffectively. No abnormalities were found on relevant physical examination. Then, the CT and MRI demonstrated a 3.3-4-cm soft tissue mass shadow in the neck of the gallbladder. The primary lesions consisted of two components: high-grade intraepithelial neoplasia of glands and hepatoid glands microscopically after laparoscope cholecystectomy. Immunohistochemical staining showed the sameness and difference of the two areas. Furthermore, tumor mutational burden (TMB) shows that the MB21D2, GALNT12, and ARID2 genes were mutated.

CONCLUSION

This is the first report of primary hepatoid adenocarcinoma of the gallbladder with MB21D2, GALNT12, and ARID2 mutations. This will provide a theoretical basis for genetic changes in rare tumors.