Seminomas and dysgerminomas are very similar tumors but differ in two significant respects: the most common age of presentation in men is in the fouh decade, while in women, it is in the third decade. Also, seminomas are relatively common in men (30% of testicular germ cell tumors), while dysgerminomas are rare in women (1% of ovarian tumors). Both of these tumors are composed of sheets of uniform polyhedral cells with intervening fibrous septa of connective tissue, lymphocytes, and multinucleated giant cells. The number of mitoses per high-power field and ultrastructural appearance do not differ greatly between the two tumors. These tumors in pure form are very radiosensitive (90% 5-year survival), but can be much more aggressive if foci of other germ cell tumors (notably embryonal carcinoma, choriocarcinoma, and yolk sac tumors) are present. Ref: Cooper C.S., Joudi F.N., Williams R.D. (2010). Chapter 38. Urology. In G.M. Dohey (Ed), CURRENT Diagnosis & Treatment: Surgery, 13e.