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Classic Seminoma

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  • Most common type of GCT (50%).
  • Peak in 30's, almost never occur in infants.
  • 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).
  • Histology:
    • 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.

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  • 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-.