Hepatocellular Neoplasm - Not Otherwise Specified (HCN-NOS)
A Mixed Cell Tumor
HCN-NOS or "HEMNOS" (hepatocellular malignant neoplasm NOS) is a new designation that describes a subset of pediatric hepatocellular tumors with features resembling both hepatoblastoma (HBL) and hepatocellular carcinoma (HCC), but remain distinct from both.
HCN-NOS seems to arise in children older than those who typically develop HBL, and younger than those who typically develop HCC.
They are not histologically typical of either HBL or HCC.
These tumors are aggressive, and with current treatment paradigms, are associated with outcomes intermediate to HBL (better) and HCC (worse) .
The history of this new subtype of hepatocellular cancer is fairly recent, tracing back to a paper in 2002 by Prokurat et al. that first proposed the distinction, naming it at the time "transitional liver cell tumors" (TLCTs). As more research was conducted, the name of this condition was changed. It is now called "hepatocellular neoplasm - not otherwise specified", an ungainly, but perhaps more accurate description of this new cancer.
Prokurat and his colleagues, from the Institute of Pathology of the University in Bern and The Children's Memorial Health Institute in Warsaw, began to characterize a type of hepatocellular tumor that seemed to fit neither of the two most common types of hepatocellular cancers seen in children. These two most common types of primary hepatic neoplasms were and still are hepatoblastoma (HBL), which tends to arise in younger children, and hepatocellular carcinoma (HCC), which tends to arise in older children and adolescents.
Through seven cases, Prokurat and his colleagues outlined features of this tumor. Ranging broadly from 5 to 18 years of age, all but one of these patients were initially diagnosed with HBL, but the unusual age of presentation and poor clinical outcomes were what elicited further attention to these cases.
López-terrada D, Alaggio R, De dávila MT, et al. Towards an international pediatric liver tumor consensus classification: proceedings of the Los Angeles COG liver tumors symposium. Mod Pathol. 2014;27(3):472-91.
Meyers RL, Maibach R, Hiyama E, et al. Risk-stratified staging in paediatric hepatoblastoma: a unified analysis from the Children's Hepatic tumors International Collaboration. Lancet Oncol. 2017;18(1):122-131.
Prokurat A, Kluge P, Kościesza A, Perek D, Kappeler A, Zimmermann A. Transitional liver cell tumors (TLCT) in older children and adolescents: a novel group of aggressive hepatic tumors expressing beta-catenin. Med Pediatr Oncol. 2002;39(5):510-8.