Hepatoid prostatic carcinoma with adrenal metastasis and novel genetic alterations.

Hepatoid carcinoma (HC) encompasses epithelial extrahepatic tumors exhibiting features of hepatocellular carcinoma (HCC) both by morphology and immunohistochemistry. Distinguishing metastatic HCC from HC may be challenging, particularly when limited material, such as a cytologic specimen, is available. HC from prostatic origin is unusual and has only rarely been characterized by cytology. Herein we present an 86-year-old male with history of castration-resistant prostate cancer developing a left adrenal gland nodule. Fine needle aspiration revealed a poorly differentiated malignant neoplasm diagnosed as metastatic hepatoid prostatic adenocarcinoma based on immunohistochemistry (positive for HepPar1, AFP, NKX3.1, PSMA, and Racemase; and negative for CK7, CK20, cytokeratin 34betaE12, p63, and Arg-1). Because prostatic carcinoma with hepatoid features is rare, and the patient had failed standard therapy, next generation sequencing was performed in an attempt to identify druggable molecular targets. Well-known prostate carcinoma-related alterations were found in three genes (CDK12, AR, and SPOP). In addition, three variants of uncertain significance (DDR2 R128C, SRC P428L, and HNRNPU K574Sfs*32) were identified, which to the best of our knowledge have not been previously reported. Our results support the power of an immunohistochemistry panel including Arg-1 and HepPar1 when HC is suspected, and highlight the value of cytology for comprehensive diagnostic evaluation.