Hepatoid Adenocarcinoma of the Stomach: A Rare Tumour in an Unusual Subserosal Location

Abstract

Hepatoid Adenocarcinoma (HAC) is a special type of adenocarcinoma of extrahepatic origin that has overlapping features with Hepatocellular Carcinoma (HCC). Herein, present case is of a 75-year-old man who presented with abdominal pain, bilious vomiting, and constipation for four days, along with a palpable mass in the abdomen for five months. Imaging studies revealed a mass in the subserosal region of the greater curvature of the stomach. Intraoperative findings showed a mass involving the stomach, liver, and omentum, initially suggesting a diagnosis of malignant Gastrointestinal Stromal Tumour (GIST). However, histopathological examination revealed lobules of polygonal cells with abundant eosinophilic to vacuolated cytoplasm and enlarged, moderately pleomorphic nuclei, indicating hepatoid differentiation. The aggressive nature of the lesion, invading the liver and omentum, the absence of risk factors for HCC, negative staining for CD 117 and polyclonal Carcinoembryonic Antigen (pCEA), and positive staining for glypican 3 and CK 19 on immunohistochemistry, confirmed the diagnosis of HAC of the stomach rather than HCC. After surgery, the patient was referred to an Oncology centre. An accurate diagnosis of HAC is crucial due to its aggressive nature and poor prognosis.