Yolk Sac Tumor : Solid Pattern

Comments:
Solid pattern in Yolk Sac Tumor (YST): It consists of polygonal tumor cells with abundant pale eosinophilic or clear cytoplasm arranged in solid nodules and sheets. The tumor cells have distinct cytoplasmic membranes and pleomorphic nuclei.

Blastema-like foci composed of small round blue cells may be present. Solid pattern of YST can mimic dysgerminoma; features favoring YST over dysgerminoma include: absence of fibrous septa and lymphocytic infiltrate, heterogenous architecture, primitive nuclei, hyaline bodies, strong and diffuse positivity for cytokeratin and AFP, positivity for glypican-3, and negative for OCT4; CD117 not helpful as 50% of solid yolk sac tumors are positive as are most dysgerminomas.