Table 1.

Histologic classification of hepatoblastoma (adopted from references [3,5]).

Type	Subtype and/or Properties
Epithelial
Fetal	• Well-differentiated: uniform with round nuclei, cords with minimal mitotic activity; may be associated with EMH * • Crowded: mitotically active, prominent nucheoli • Pleomorphic: poorly differentiated, high nuclear:cytoplasmic ratio; moderate anisonucleosis • Anaplastic: marked nuclear enlargement, pleomorphism and hyperchromosia; abnormal mitoses
Embryonal	Smaller cells; high nuclear:cytoplasmic ratio; primitive tubules may be associated with EMH
Macrotrabecular	Fetal or embryonal type growing in clusters of 5 or more cells between sinusoids
Small cell undifferentiated	About half the size of fetal HB; minimal pale & amphophillic cytoplasm; oval/round nuclei; fine chromatin; inconspicuous nucleoli
Cholangioblastic	Presence of bile ducts that may be quite prominent
Mixed
Stromal derivative	Spindle cells/blastema; presence of other components (osteoid, cartilage, muscle)
Teratoid	Mixed; primitive endoderm; presence of neural derivatives; squamous and/or glandular components, melanin

* EMH: extramedullary hematopoiesis.