Embryonal Carcinoma Involving the Ovary: A Morphologic Study of 55 Tumors Almost Never Pure, But Common Within Malignant Mixed Germ Cell Tumors.

Pure ovarian ECA is rare; none were identified in our series. Many purported pure examples are likely undersampled MMGCTs or other tumor types (yolk sac tumor, dysgerminoma [particularly when poorly fixed], small cell carcinoma of hypercalcemic type, juvenile granulosa cell tumor, and high-grade surface epithelial carcinomas). The diagnosis can be made on the basis of morphologic criteria and, in problematic cases, supported by immunohistochemistry.