Five cases of
yolk sac tumor of the anterior mediastinum associated with prominent thymic cystic changes are presented. The patients were five men between the ages of 17 and 22 years (mean, 19.5 yr). Clinically, four patients presented with symptoms of
chest pain and
shortness of breath, whereas the fifth was asymptomatic: his
tumor was discovered during a routine physical examination. None of the patients had a history of previous
tumor elsewhere. Grossly, the
tumors were described as cystic lesions measuring between 8 and 12 cm in greatest dimension. Histologically, the
tumors showed prominent cystic changes reminiscent of those observed in acquired multilocular
thymic cysts, i.e., the presence of cystic cavities lined by squamous epithelium with prominent inflammatory changes, lymphoid
hyperplasia,
cholesterol cleft
granulomas, and remnants of thymic tissue in the walls of the
cysts. In addition, there was a neoplastic cellular proliferation composed of small cells with scant cytoplasm, round nuclei, and inconspicuous nucleoli adopting a reticular pattern of growth and, in some areas, embedded in abundant myxoid stroma. Numerous intra- and extracellular hyaline globules, as well as Schiller-Duval bodies, could also be identified. Immunohistochemical studies showed positive reaction with
alpha-fetoprotein antibodies in the
tumor cells. Follow-up information obtained in these patients showed that all had died of
tumor 1 to 3 years after initial diagnosis. The present cases document another unusual but distinctive growth pattern of
yolk sac tumor in the mediastinum and highlight the importance of proper sampling of cystic lesions in this location.