Fine-needle aspiration biopsy diagnosis of endodermal sinus tumor: histologic and ultrastructural correlations.

Fine-needle aspiration biopsies from five patients with endodermal sinus tumors (ESTs) were reviewed, and the findings were correlated with histologic and ultrastructural appearances. In the aspiration smears, two types of tumor cells were seen, forming clusters of variable sizes. Type A cells had distinct cell borders, and their cytoplasm contained only occasional vacuoles. Type B cells had ill-defined cell borders and formed syncytial clusters; their cytoplasm was characterized by large numbers of rounded vacuoles. The background contained patches of mucoid material and macrophages with foamy cytoplasm. Eosinophilic hyaline cytoplasmic bodies and irregular deposits of intercellular basement membrane-like material were recognized easily in aspiration smears. These features correlated well with histologic and ultrastructural appearances. The significance of these findings in the fine-needle aspiration biopsy diagnosis of EST and its distinction from other germ-cell and non-germ-cell tumors is discussed.