Yolk Sac Tumor : Microcystic Pattern
Small cystic spaces lined by flattened endothelium-like or cuboidal cells. Immunohistochemically, yolk sac tumors show diffuse granular positivity for AFP and keratin. A combination of SALL4 positivity and OCT3/4 negativity is considered to be highly specific for yolk sac tumor. GATA-4, a transcription factor, is expressed in pediatric cases.