Answer: Adrenal cortical carcinoma

Histology: The tumor is essentially a sheet like proliferation of polygonal eosinophilic cells. The tumor cells have irregular, hyperchromatic nuclei with prominent nucleoli. Prominent nuclear atypia is seen and mitoses are readily apparent. Atypical mitoses are also present focally. By immunohistochemistry, the tumor cells label for Melan-A and inhibin, along with synaptophysin, but not for chromogranin or HMB45. These results support the diagnosis of adrenal cortical carcinoma.

Discussion: Metastatic hepatocellular carcinoma can mimic adrenal cortical carcinoma. The absence of labeling for Hepar-1, along with the labeling for Melan-A and inhibin argue against hepatocellular carcinoma. The current neoplasm is distinguished from an adrenal cortical adenoma because it meets more than three of the Weiss histologic criteria for malignancy, including high nuclear grade, high mitotic rate (greater than 5 mitoses per 50 high-power fields), atypical mitoses, diffuse growth pattern, venous invasion, and less than 25% clear cells. Necrosis, capsular invasion and sinusoidal invasion were absent in this neoplasm. Paraganglioma may be suggested by the synaptophysin immunoreactivity, but it is important to know that synaptophysin labeling may be seen in adrenal cortical carcinomas. Importantly, adrenal cortical carcinomas are always negative for chromogranin.