Department of Pathology, Dankook University College of Medicine, Cheonan, Korea. firstname.lastname@example.org
Diffuse embryoma of the testis is a very rare, distinct form of mixed germ cell tumor. I report here on a case of diffuse embryoma in a 22-year-old male who presented with painful scrotal swelling. The resected testis was entirely occupied by a non-encapsulated tumor mass. The cut surface of the tumor was grey or whitish pink, soft and granular with foci of hemorrhage and necrosis. Microscopically, the tumor was characterized by a diffuse, orderly arrangement of embryonal carcinoma and yolk sac tumor in almost equal proportions.
The yolk sac tumor component was diffusely wrapped around the embryonal carcinoma. Syncytiotrophoblasts were scattered throughout the tumor. Minor foci of immature teratoma, seminoma and intratubular germ cell neoplasia were observed.
The yolk sac tumor (YST) component was emphasized by immunoreactivity for alpha fetoprotein, whereas the embryonal carcinoma was reactive for CD30. The strong reactivity for cytokeratin in the YST component formed an outstanding contrast to the weak cytokeratin reactivity in the embryonal carcinoma.