A baby is born with a testicular mass. Histologic sections made of the homogeneous yellow white mass after its removal demonstrate epithelial-lined spaces that have flattened-to-cuboidal epithelial cells with vacuolated cytoplasm containing eosinophilic, hyaline-like globules. Scattered structures resembling primitive glomeruli (endodermal sinuses) are also seen. If appropriate immunohistochemical stains are performed, the eosinophilic cytoplasmic globules would most likely contain which of the following?