Hepatocellular Malignant Neoplasm, Not Otherwise Specified: A New Name in Liver Tumors: A Brief Narrative Review of Published Cases.

Background: Hepatocellular malignant neoplasm, not otherwise specified (HEM, NOS), is a rare liver tumor that is most commonly seen in adolescents. To the best of our knowledge, there has been no published review on this rare tumor in the English literature so far.

Summary: In this review, we will discuss all reported details, including demographic findings, clinical presentations, molecular histogenesis, imaging, gross pathology and histopathology, immunohistochemical findings, treatment modalities, and outcome, of the published cases of HEM, NOS, in the liver.

Key message: Twenty-two cases of HEM, NOS, have been reported in the last 10 years in the English literature. This tumor produces a large liver mass and is characteristically seen in adolescents presenting with right upper quadrant pain. Histologically, HEM, NOS, is a nonbiliary hepatocytic tumor with a biphasic pattern, that is, a mixture of 2 components of hepatocellular carcinoma and hepatoblastoma (HBL). There is no characteristic immunohistochemical feature for this tumor. Imaging findings are also not specific. Treatment of this tumor needs extensive surgery or even liver transplantation. Most of the cases in the literature were treated with the primary diagnosis of HBL, so pathologists, onco-surgeons, and oncologists should get familiar with this tumor to provide better treatment options. More case series with more follow-ups are necessary for the definite determination of the outcome of this tumor as a unique entity.