Hepatoblastoma

 Pure fetal epithelial histology is associated with favorable prognosis


image Embryonal and fetal epithelial patterns often seen together

image Macrotrabecular is composed of fetal or embryonal type cells in wide trabeculae

image Small undifferentiated component is associated with poorer prognosis


• Mixed hepatoblastoma (HB) are composed of epithelial and mesenchymal components
image Mesenchymal component can range from immature spindle cells to fibrous tissue

image Osteoid-like and teratoid elements can occur




Ancillary Tests




• Nuclear β-catenin staining in epithelial and mesenchymal components (70% of cases), often membranous in fetal pattern

• Positive glypican-3 and Hep-Par1 staining in fetal and embryonal epithelial cells

• Positive glutamine synthetase staining in fetal and variably in embryonal cells


Top Differential Diagnoses




• Normal liver parenchyma; positive nuclear &/or cytoplasmic β-catenin staining in HB

• Hepatocellular carcinoma; presence of both fetal and embryonal patterns diagnostic of HB

image
Treated Hepatoblastoma, Gross
This tumor was treated with preoperative chemotherapy and was diagnosed as a mixed epithelial and mesenchymal hepatoblastoma with teratoid features. The black focus image contained melanin pigment.


image
Embryonal Pattern
H&E shows sheets and poorly formed nests of embryonal epithelial cells with angulated nuclei and less cytoplasm than fetal epithelial cells, which can often coexist in the same tumor. Embryonal cells have nuclear or cytoplasmic reactivity to β-catenin and are diffusely positive for glypican-3.

image
Pure Fetal Histology
H&E shows uniform polygonal cells that are smaller than normal hepatocytes with round nuclei, no nucleoli, clear cytoplasm, and no mitotic activity.

image
Pure Fetal Histology
Light and dark appearance is due to variable amounts of glycogen or cytoplasmic lipid. If the entire tumor has this appearance and mitotic activity ≤ 2/10 HPF, it would be classified as pure fetal histology.


TERMINOLOGY


Abbreviations




• Hepatoblastoma (HB)


Definitions




• Predominantly pediatric liver tumor that mimics developing fetal or embryonal liver histologically


ETIOLOGY/PATHOGENESIS


Neoplasm




• Wnt pathway activation in 70-90% due to β-catenin mutation


CLINICAL ISSUES


Epidemiology




• Incidence
image 2.1% of all pediatric cancers (1-19 years)

image Higher in low birth weight infants

• Age
image Most common malignant liver neoplasm in children
– 88% in children ≤ 5 years and 3% > 15 years

– Mean age at diagnosis is 19 months

• Sex
image Male predominance (M:F = 3:2)


Site




• 58% involve right lobe, 27% involve both lobes


Presentation




• Painless abdominal mass, hepatomegaly


Laboratory Tests




• Increased serum α-fetoprotein in 75-96% of patients
image Often ≥ 100,000 ng/mL

image Caveat: High AFP normal before 6 months of age

image Useful marker of response to therapy and recurrence


Treatment




• Surgical resection
image Stage 1 pure fetal HB cured by surgical resection alone

image Only 1/3 to 1/2 have resectable disease at presentation

image Preoperative chemotherapy converts > 50% of inoperable tumors to resectable tumors

image Children’s Oncology Group (COG) standard regimen consists of cisplatin, 5-fluorouracil, and vincristine (C5V)

• Liver transplant considered in unresectable cases


COG Staging System (Pretreatment Staging)




• Stage I: Completely resected tumor with negative margin
• Stage II: Grossly resected tumor with microscopic residual tumor (positive margin)

• Stage III: Unresectable tumor

image Biopsy diagnosis, partially resected, macroscopic residual tumor, tumor rupture

image Positive abdominal lymph node

• Stage IV: Metastasis to lungs, other organs, or sites distant from abdomen


Prognosis




• Tumor stage is key prognostic factor in survival
image 90% event-free survival with complete tumor resection

image < 70% event-free survival with nonmetastatic, unresectable tumor


Metastasis




• 10-20% of patients have metastases at presentation

• Lung most frequent, but can involve bone, brain, eye, or ovaries

• 20-30% survival with metastatic disease at presentation


Conditions Associated With HB




• Familial adenomatous polyposis, Beckwith-Wiedemann, Li-Fraumeni, Simpson-Golabi-Behmel syndromes

• Trisomy 18, glycogen storage disease types I-IV, hemihypertrophy


IMAGING


Radiographic Findings




• Solitary or multifocal mass
image Heterogeneous and hypervascular

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Apr 20, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Hepatoblastoma
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