Cytomorphology of yolk sac tumor of the liver in fine-needle aspiration: a pediatric case.

Yolk sac tumors (YST) in extragonadal locations are rare. Cytologic diagnosis of YST on fine-needle aspiration (FNA) smears may be a challenge to the cytopathologist. Further neo-adjuvant therapy may be based on cytologic diagnosis making accuracy important. We studied FNA material from a hepatic mass in a pediatric patient to further define the cytomorphologic features of hepatic YST. Features include large pleomorphic balls of tumor cells with high nuclear to cytoplasmic ratios, papillary or microglandular pattern of growth, cytoplasmic and intranuclear vacuoles, and prominent nucleoli. Positive immunohistochemical studies included alpha-fetoprotein, cytokeratin AE1/AE3, and CAM 5.2, which are useful in supporting the diagnosis. We report a pediatric patient in whom the diagnosis of hepatic YST was made by cytologic, histologic, and immunohistochemical studies. The subsequent liver biopsy was consistent with the FNA diagnosis. Our findings may further help to characterize the cytomorphologic features of this rare lesion.