Morphologically identical tumor in ovary is called "dysgerminoma".
Gross: typically well-circumscribed with homogenous, gray-white, lobulated cut surface and usually NO necrosis or hemorrhages (mean 5.0 cm).
Uniform tumor cells with abundant clear cytoplasm, distinct cell border, and large central nuclei with prominent 1-2 nucleoli (image A), (image B), & (image C).
Separated into nests by fibrous septa.
Lymphocytic and plasmacytic infiltrates in fibrous septa.
Multinucleated giant cells (syncytiotrophoblasts) may be seen, especially in patients with elevated HCG.
Granulomatous inflammation can occur in ~1/3 and when extensive may cause problems in diagnosis.
Immunohistochemistry: PLAP+, Oct3/4+ and CD117+ (image D), and keratin-.
Excellent prognosis with >95% cure rate for stage I and II.
Main differential diagnosis: (other GCTs that can have solid growth)
Embryonal carcinoma: exhibits cellular pleomorphism and nuclear overlap, CD30+ and keratin+.
Solid yolk sac tumor: other patterns of yolk sac present, AFP+ and glypican-3+.
Spermatocytic seminoma: older patients, with polymorphic cells (3 cell types), Oct3/4- and PLAP-.