An ectopic adrenocortical oncocytic adenoma in the liver highly mimicking hepatocellular carcinoma: case report and literature review

Background Ectopic adrenocortical tissue is a lesion usually found incidentally during autopsy or inguinal surgery. Here, we demonstrate an extremely unusual case of intrahepatic adrenocortical adenoma which highly mimicks hepatocellular carcinoma (HCC) and brings challenges for clinicians and pathologists. The diagnostic pitfalls have been discussed in detail to provide clues for guiding differential diagnosis and future treatment. Case presentation A 44-year-old man was admitted into our hospital for evaluation of a hepatic mass identified during routine examination. Enhanced CT revealed its margin displayed apparent enhancement in arterial phase, but hypointensity in portal and delayed phase. HCC was suspected and partial hepatectomy was performed. Microscopically, cells were arranged in solid sheets. Most of the tumor cells were large, polygonal, had prominent nucleoli and were rich in eosinophilic cytoplasm. Pleomorphic nucleus was frequently found. Focally, smaller cells were found with small nuclei and granular cytoplasm. Immunohistochemically, tumor cells were negative for Arg-1, glypican-3 (GPC3), hepatocyte specific antigen (HSA), and positive for synaptophysin (Syn), α-inhibin, and Melan A. The Ki-67 index was 1 %. The final diagnosis was ectopic adrenocortical oncocytic adenoma and the patient was uneventful after the surgery. Conclusion Intrahepatic adrenocortical adenoma in the liver can hardly be diagnosed through radiology and little experience in pathology has been reported. In the present case, massive oncocytic changes and huge pleomorphism add greatly to the difficulties of making correct diagnosis. This lesion should be carefully kept in mind and a combination of markers is suggested for differentiating from HCC.