Hepatoblastomas (HB) are the most common pediatric liver tumor with several subgroups described, of which teratoid HB is the rarest. The aim of this study is to characterize the histologic and phenotypic spectrum of teratoid HB in order to better understand the biology and behavior of these tumors. A retrospective analysis of all teratoid HB diagnosed at a major pediatric hospital as well as the consultation files of one of the authors (SR) was performed with the available clinical data and surgical pathology material reviewed. A detailed immunohistochemical workup was also performed. A total of 28 cases were included from patients ranging from 5 to 84 months of age and a M:F ratio of 1.07:1. Four patients had syndromic associations. In 14/28 cases, the tumors contained primitive glandular elements with histologic and immunophenotypic overlap with the yolk sac tumor which in two cases became predominant in metastatic sites. One case had extensive primitive neural epithelium mimicking a primitive neuroectodermal tumor (PNET). Other unique elements included melanin, mature neuroglial tissue, rhabdomyoblastic differentiation, and neuroendocrine carcinoma-like areas (n = 2). In conclusion, this study provides the largest series of teratoid HB to date with clinical and outcome data, highlights previously undescribed or under-recognized histologic patterns in these tumors, and describes the immunohistochemical profile of these tumors to aid in diagnosis.

Purpose and Context: Glypican-3 is often used to discriminate between neoplastic and nonneoplastic liver. In focal lesions, positivity may be considered suggestive of a malignancy such as hepatoblastoma. However, glypican-3 is also normally expressed in the immature liver. We present a series of 5 cases of focal nodular hyperplasia (FNH)-like lesions arising in very young patients with glypican-3 expression and highlight the challenges these lesions present in the differential diagnosis of hepatoblastoma. Methods: Cases were obtained from the files of 3 tertiary pediatric hospitals. Clinical data were obtained from the electronic medical record and histopathologic material including immunohistochemical stains were reviewed. Key Results: Patients were aged 2 weeks to 6 months with peak AFP levels ranging from 88.6 to 204,696 ng/mL. Microscopically, all were variably demarcated hepatocellular lesions with cords of hepatocytes, marked sinusoidal dilatation, and occasional fibrous bands and areas reminiscent of central scar with bile ducts. No significant cytologic atypia or increased mitotic activity were present. All showed glypican-3 expression and were negative for nuclear beta-catenin with intact reticulin framework. Conclusions: Our study highlights the pitfalls of evaluating focal liver lesions in infants when high AFP levels and glypican-3 expression may reflect immaturity rather than neoplasia.

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