Most common testicular tumor in infants and young children.
2 age peaks:16-18 months (Pure YST) and 25-35 years old (YST in mixed GCT).
Pure YST in pediatric patients is not associated with ITGCN or cryptorchidism; extremely rare in adults.
>95% of YST patients have elavated serum AFP level (100's-1000's ng/ml).
Gross: gray white tumors with myxoid or gelatinous cut surface; +/- hemorrhage in adults because it is usually part of a mixed GCT (image A).
Histology: multiple or variable growth patterns (12 patterns):
Most common are microcystic, solid and myxomatous.
Microcystic or reticular most frequent (80%) – multiple intercellular holes imparting a "sieve-like" pattern (image B).
Other uncommon patterns include endodermal sinus, papillary, polyvesicular vitelline (vesicles lined by flattened and cuboidal cells), glandular, parietal, enteric, hepatoid, spindle and mixed patterns.
Image C (click on the image above)
Image D (click on the image above)
Relatively uniform cells with clear or vacuolated to lightly eosinophilic cytoplasm.
Endodermal sinus pattern composed of Schiller-Duval bodies, which resembles primitive glomeruli (Central vessel encircled by tumor cells, a space, and surrounded by another layer of flat tumor cells)
Hyaline-like globules, which contain AFP and a1-antitrypsin, can be seen (image D).
Immunohistochemistry: AFP+ and glypican-3+
Childhood YST has better prognosis than adult YST.
Mixed GCTs with or without YST are treated similarly.