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Of all malignant intratesticular neoplams, mixed germ cell tumors are the second most common. Of these the majority are at least a portion of embryonal cell carcinoma which constitute 20-25% of all primary germ cell malignancies. Unfortunately this subtype of germ cell tumor tend to be more aggressive and will invade the tunica albuginea and/or cause visceral metastases. Although embryonal cell carcinomas have three sub-types: adult, infantile and endodermal sinus tumor, embryonal cell carcinomas tend to be less radio and chemosensitive than seminomatous tumors. Infantile and endodermal sinus types are associated with elevated alpha-fetoprotein which can be used to monitor therapy/recurrence.
Teratomas are a second type of germ cell tumor. Teratoma also has three subtypes: mature, immature, and with malignant transformation. Teratomas must have three germinal layers: endoderm, mesoderm, ectoderm. They constitute 5% of all primary testicular neoplasms. Although approximately 30% will metastasize, the reported 5-year survival is 70%.
Although not seen in this case the other type of non-seminomatous germ cell tumor type is choriocarcinoma which is the rarest and least favorable of the three basic types. Although it rarely occurs in its pure form, it represents 23% of mixed germ cell tumors. These leisons are highly vascular and metastasize early.