DEMONSTRATION OF FIBRILS IN THE HYALINE GLOBULES OF YOLK-SAC TUMOR WITH PARIETAL DIFFERENTIATION IN FINE-NEEDLE ASPIRATION SMEARS

Hyaline globules of the yolk sac tumor (YST) have been described as ho mogeneous pink intracellular globules and intercellular basement membr ane material [Akhtar et al.: Diagn Cytopathol 1990;6:184-192]. In Diff -Quik-stained air-dried smears of a lung fine-needle aspiration (FNA) of YST metastatic from anterior mediastinum, short curvilinear nonbran ching fibrils are demonstrated in the metachromatic hyaline substance. The fibril-containing hyaline substance, which presents as intracellu lar globules as well as extracellular matrix deposits, is a diagnostic clue for YST with parietal differentiation [Ulbright et al.: Am J Sur g Pathol 1986;10:151-164]. The fibrils are not observed in the translu cent homogeneous golden yellow hyaline substance in the Papanicolaou p reparation. The fibrils are speculated to be the core protein of prote oglycans. To the best of the author's knowledge, this is the first dem onstration of fibrils in the hyaline substance of YST with parietal di fferentiation. (C) 1994 Wiley-Liss, Inc.