Surgical removal of the mediastinal mass and four regional lymph nodes and pleural nodule.

Histology

MICROSCOPIC FEATURES:

Mediastinal mass: Sections show a non-seminomatous mixed germ cell tumor showing extensive tumor necrosis. The percentage of viable tumor tissue is estimated to be approximately 20%. 100% of the viable tumor is a yolk sac tumor showing a variety of patterns including some cystic areas with hyaline globules in cells lining a cyst. Schiller-Duval bodies are readily identified. The left-sided soft grey nodule is a keratin-filled cyst surrounded by entirely necrotic tissue consistent with entirely necrotic teratoma. No immature teratoma component is identified. A few foci showing larger more pleomorphic cells are present which are the pleomorphic cell type pattern of yolk sac tumor (alpha-fetoprotein positive,  CD30 and beta-HCG negative). There is no evidence of embryonal carcinoma, seminoma or choriocarcinoma on routine or immunohistochemistry stains. Alpha-fetoprotein stain shows only a few foci of positivity within the yolk sac tumor.

Pleural nodule: Sections show both viable and necrotic yolk sac tumor with a small amount of attached diathermied skeletal muscle. Focally viable yolk sac tumor abuts an inked margin immediately adjacent to an area of diathermied margin, over a distance of approximately 5 mm

Lymph nodes: no viable tumor

FINAL DIAGNOSIS: 

1. Mediastinal tumor - non-seminomatous mixed germ cell tumor.
2. Approximately 20% of tumor tissue viable.
3. 100% of the viable tumor is yolk sac tumor. Entirely necrotic teratoma also present. No immature teratoma identified.