Hepatoblastoma is a rare, but the most common hepatic malignancy of childhood with a peak incidence from 6 months to 3 years. The etiology of hepatoblastoma is unknown, but it has been associated with Wiedemann-Beckwith syndrome, familial adenomatosis polyposis coli, prematurity and low birth weight. Hepatoblastomas are well-defined, solid, mostly intrahepatical lesions. Lymphatic and hematogenic metastases occur in advanced disease stages with the latter mostly involving the lungs. AFP levels are nearly always elevated in hepatoblastomas and are correlated in most cases with the stage of the disease ; also the rate of decline of AFP during treatment is of prognostic value. The decrease of AFP during chemotherapy, despite an increase in tumor size in our case, is at first sight unusual, but most likely reflects a rather high chemosensitivity of the hepatoblastoma tumor portions. In the teratoma, areas kept proliferating and were hardly affected. Correspondingly, the cells in the areas of tumor necrosis were at least in part still positive for HepPar-1.
Teratomas are rare neoplasms (incidence 0.7/100.000 children/year) with tissue derivatives of all three germ layers. Teratomas mostly occur in the ovaries, the sacrococcygeal region, the testes, and the central nerval system and only rarely in other locations with less than 5% occurring in the abdomen . Teratomas are thought to have been present since birth, or even before birth, and are therefore considered as congenital tumors. In the liver, only single cases of (benign or malignant) teratomas have been described [1–4].
Our case represents a nearly unique combination of both tumor entities, hepatoblastoma and malignant teratoma in a young boy. Though mesenchymal tumor portions can occur within hepatoblastomas, most commonly osteoid or chondroid , our case is different as it presents a large spectrum of mesenchymal and epithelial differentiation pattern in most of the lesion. Obviously, the dispute whether to call such a lesion mixed hepatoblastoma and teratoma or teratoid hepatoblastoma  might be mostly semantic. In our case, in which most of the lesion represented teratoma, however, we clearly prefer to talk about a mixed or combined neoplasm, namely mixed hepatoblastoma and teratoma.
The treatment of the presented mixed hepatoblastoma and teratoma of the liver was based on a combined systemic chemotherapy and surgery. Therapies of such a mixed tumor tissue have not been described yet, but children with hepatoblastomas have nowadays, due to the new therapy modalities, a rather good prognosis with a 5-year survival rate of over 70%  with curative surgery being the primary treatment of all pediatric liver tumors especially in the absence of metastatic disease. Systemic chemotherapy is beneficial as metastases are detectable at diagnosis in about 20% of all patients and most children suffer tumor recurrence after surgery alone.
In summary, we report on the diagnosis and clinical management of to our knowledge the second case of a mixed hepatoblastoma and teratoma in a young boy . Clearly, this represents a rare facet of embryonic tumors within the liver. This case as well as similar cases with a very peculiar tumor biology  documents the importance of adequate sampling of tumor material in all cases of heterogenous tumor differentiation in order not to miss minor, but relevant tumor portions. Management, as far as it can be estimated from a single case, appears to be along the guidelines valid for hepatoblastoma alone with, however, the caveat that the (applied) chemotherapy was only effective in the hepatoblastoma areas and not the teratoma portion of the tumor.