Germ cell tumor differential diagnosis

• Cytoplasmic membrane immunoreactivity for placental alkaline phosphatase and CD117, with usual negativity for AE1/AE3 cytokeratins, is helpful in the diagnosis of germinoma.
• The recently described marker, OCT3/4, a nuclear transcription factor, is especially helpful in the differential of germinoma and embryonal carcinoma with other neoplasms.
• Yolk sac tumor continues to be confused occasionally with clear cell carcinoma of the ovary.
• Glandular ('endometrioid-like') yolk sac tumors mimic endometrioid carcinomas
• Predominant or pure hepatoid yolk sac tumors cause concern for metastatic hepatocellular carcinoma or, in the ovary, primary hepatoid carcinoma, and solid patterns, especially in limited samplings, may be misinterpreted as germinoma
• The usually younger age of patients with yolk sac tumors helps with the differential considerations with the nongerm cell tumors, as do other clinical and microscopic features and selected immunohistochemical stains.
• Choriocarcinoma is rare in both gonads, and those in the ovary must be distinguished from metastatic tumors of placental origin
• Syncytiotrophoblast cells alone, admixed with other forms of germ cell tumor, still are confused with choriocarcinoma, but this phenomenon, which is much more frequent than choriocarcinoma, lacks the plexiform arrangement of different trophoblast cell types that typifies the latter