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

Abstract

Embryonal carcinoma (ECA) of the ovary is rare, particularly in pure form, with very limited available information. To expand on knowledge by reviewing our experience. We report 55 tumors with an ECA component in patients from ages 3 to 57 years (median, 20.5 years), with emphasis on their pathologic features. The tumors ranged from 2.5 cm to 31 cm (average, 15.4 cm), being predominantly solid and cystic with hemorrhagic necrosis. In all cases, the ECA was a component of a malignant mixed germ cell tumor (MMGCT) and represented less than 15% in 22 tumors (40%), 16% to 50% in 22 (40%), 51% to 75% in 6 (11%), and greater than 75% in 5 (9%). Components admixed with the ECA included yolk sac tumor (n = 49; 89%), immature teratoma (n = 34; 62%), dysgerminoma (n = 20; 36%), and choriocarcinoma (n = 5; 9%). The most common microscopic patterns of the ECA were glandular (n = 24; 45%), solid (n = 19; 35%), papillary (n = 5; 9%), and micropapillary (n = 1; 2%). Embryoid bodies, or remnants thereof, were present in 16 tumors (29%), and 6 (11%) had a diffuse embryoma pattern. Apoptotic bodies were commonly found. A lymphocytic infiltrate and granulomas were seen in 25 tumors (45%) and in 4 tumors (7%). 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.