embryonal carcinoma /em″brē·ənəl/ , a malignant neoplasm derived from germinal cells that usually develops in gonads, especially the testes. The tumor, a firm nodular mass with hemorrhagic areas, is characterized histologically by large, undifferentiated cells with indistinct borders, eosinophilic cytoplasm, and prominent nucleoli in pleomorphic nuclei. Bodies resembling a 1- or 2-week-old embryo are occasionally seen in these tumors. The neoplasm is relatively resistant to radiation therapy. The tumor metastasizes by way of lymph channels. Surgery and chemotherapy are usually used in the treatment. See also choriocarcinoma.
