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Case Presentation - Summer, 2006

Hepatoblastoma

NOTE: The diagnosis and analysis for this case study were provided by an independent physician. All conclusions and opinions are those of the physician and not Hologic, Inc.

History: 3-year-old female

Specimen type: Peritoneal Fluid

Case provided by: Lab would like to remain anonymous

Cytologic diagnosis: Consistent with Hepatoblastoma

Liver biopsy: Hepatoblastoma

Discussion
Hepatoblastoma is the most common malignant liver tumor in infants and young children, comprising 60-85% of all hepatic tumors. It typically presents from infancy to age five, with most patients being younger than three years old and affects boys twice as often as girls. The tumor presents as an enlarging asymptomatic abdominal mass. Depending on the size of the tumor and the location of possible metastases, later symptoms can include weight loss, decreased appetite, abdominal pain, vomiting, jaundice, fever, itching skin, anemia and back pain.

Two histologic types of hepatoblastoma are described: the epithelial type and the mixed epithelial type. The epithelial type comprises 56% of all tumors and contains four subtypes including pure fetal subtype (31%), embroynal subtype (19%), macrotrabecular subtype (3%) and small cell undifferentiated subtype (3%). The pure fetal subtype has the best prognosis. The mixed epithelial type features epithelial and mesenchymal components. The differential diagnosis is hepatocellular carcinoma but marked pleomorphism and giant tumor cells are not seen in hepatoblastoma.

Treatment and prognosis
Hepatoblastoma is curable by complete resection of the tumor. However, resection may not be an option if the tumor is very large (causing it to be more likely to hemorrhage), both right and left lobes are involved, the hepatic veins are involved or the tumor contains multiple foci. The resectability of tumors increases with the use of pre-operative chemotherapy.

The five-year survival rate is nearly 100% with resection and chemotherapy. The first two years after treatment require close follow-up to guard against recurrence.

Cytology
Epithelial cells can present in various forms ranging from anaplastic to embryonal to fetal cells, representing the histologic diversity described above. Anaplastic cells are a homogenous population of small round to oval cells similar to those seen in neuroblastoma, Ewing's sarcoma and Wilm's tumor. These cells have a very high N/C ratio with scant, delicate cytoplasm. The eccentric nuclei have fine to coarse chromatin with occasional nucleoli. Mitoses can frequently be seen.

While embryonal cells are more mature than anaplastic cells, high N/C ratios are still maintained. The round to oval nuclei are hyperchromatic with coarse chromatin and prominent nucleoli. Cellular arrangements vary from rosettes, papillae, cords or ribbons. Mitoses are common.

Fetal cells are larger than embryonal cells. The larger amount of granular or clear cytoplasm in fetal cells results in a lower N/C ratio. The round to oval nuclei are slightly hyperchromatic with occasional nucleoli. Groups of fetal cells can be seen in large three- dimensional clusters, loosely cohesive small sheets and acini. Fetal cells may contain bile, fat or glycogen and mitotic figures are infrequent.

Positive immunocytochemical results are yielded for: epithelial membrane agent (EMA), cytokeratin and alpha-fetoprotein.

References
  1. www.emedicine.com Hepatoblastoma: Article by Mary Elizabeth McCarville, MD.
  2. www.lpch.org Hepatoblastoma
  3. Atkinson/Silverman: Atlas of Difficult Diagnoses in Cytopathology. 1996:513,526.
  4. Demay, Richard M: The Art and Sciences of Cytopathology. 1996:1033.
  5. Demay, Richard M: Practical Principles of Cytopathology. 1999:317.
  6. Gray/McKee: Diagnostic Cytopathology Second Edition. 2003:395
  7. Steenman M. Liver: Hepatoblastoma. Atlas Genet Cytogenet Oncol Haematol. November 2001. www.infobiogen.fr.