Fine needle aspiration cytology of hepatoblastoma. Recognition of subtypes on cytomorphology

OBJECTIVE: To delineate the cytomorphologic appearances of hepatoblastoma (HBL) in the largest series to date and to evaluate the feasibility of subtyping on fine needle aspiration cytology (FNAC). STUDY DESIGN: Papanicolaou- and May-Grünwald-Giemsa-stained smears of aspirates from 26 cases of HBL were analyzed by 2 observers. Histologic material, available in 15 cases, was correlated. A cytology grouping system was proposed on the basis of which all cases were classified. RESULTS: The ages of the patients ranged from 4 months to 9 years. Twenty-five cases were categorized as epithelial HBL, with epithelial fragments showing a trabecular arrangement and acinar formation in all, and extramedullary hemopoiesis in 20 cases. It was possible to differentiate fetal and embryonal areas on FNAC. Six cases showed only fetal elements (cytology group F), characterized by cells with abundant cytoplasm and a small, rounded nucleus resembling a normal fetal hepatocyte. The chromatin was finely granular, with a single, central nucleolus. Pleomorphism and mitoses were not seen, and the nuclear/cytoplasmic ratio was < or = 1/3. Fourteen cases showed, in addition to fetal elements, an embryonal component characterized by cells with scant cytoplasm, a pleomorphic nucleus, N/C ratio of > or = 3/1, coarsely granular chromatin and 2-4 angulated nucleoli. Mitoses were seen in these cells (1-4/1,000 cells). Of these 14 cases, 6 showed predominantly fetal and scant embryonal cells, while 8 cases showed fetal and embryonal components in equal amounts (cytology groups Fe and FE, respectively). Four cases showed predominantly embryonal cells (cytology group E). One case was unclassifiable (U). On histology, 8 of 14 cases were of mixed epithelial and mesenchymal type, but mesenchymal tissue was not seen on the corresponding cytology. The cytology grouping system correlated well with histology. One case was small cell undifferentiated HBL and resembled a round cell tumor without differentiation. Macrotrabecular arrangement was not seen on cytology but was seen on histology in 1 case. CONCLUSION: Epithelial HBL can be easily diagnosed in aspirates further classified into fetal and embryonal subtypes, which may be of prognostic relevance. The proposed cytology grouping system is effective in semiquantification of the observed subtypes.