Testis (undescended), Yolk-sac tumour, AFP stain

Yolk sac tumours are the most common testicular tumours in infants and young children. They may also occur in adults, usually as a component of a mixed germ cell tumour. Microscopically, yolk sac tumours often have a heterogenous appearance with multiple architectural patterns. This case demonstrates a mixture of microcystic, reticular, glandular/tubular, and solid patterns amongst a variably myxoid stroma. Focal areas consistent with Schiller-Duval bodies are also seen (fibrovascular cores with tumour cells, surrounded by cystic spaces and a second layer of tumour cells, resembling glomeruli). Intercellular eosinophilic globules are also seen throughout the tumour and are composed of alpha-fetoprotein (AFP) and alpha-1-antitrypsin. AFP staining by immunohistochemistry is characteristic of this tumour as seen in this slide. See Related Content section for H&E stain.