HEPATOID YOLK-SAC TUMORS OF THE MEDIASTINUM - A CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY OF 4 CASES

Four cases of primary hepatoid yolk sac tumors of the anterior mediast inum are described. The patients were all men between the ages of 26 a nd 40 years (median 33). Clinically, they all presented with a history of shortness of breath and chest pain of several weeks' duration. Non e of the patients had a history of germ cell tumor elsewhere or eviden ce of any hepatic abnormality. Grossly, all the tumors were described as large mediastinal masses that impinged on adjacent structures. Hist ologically, they were characterized by sheets of medium-sized, round t o polygonal neoplastic cells with moderate amounts of eosinophilic cyt oplasm and round to oval nuclei with prominent nucleoli. The cellular proliferation was homogeneous and displayed moderate cellular atypia a nd scattered mitotic activity All the tumors showed focally the presen ce of more conventional areas of yolk sac tumor, with islands of tumor cells showing a reticular pattern of growth admired with scattered in tra-and extracellular hyaline globules and occasional Schiller-Duval b odies. Immunohistochemical studies showed strong positivity of the tum or cells for alpha-fetoprotein in both components of the lesions. Foll ow-up information was available in three patients, all of whom develop ed lung metastases within a year after initial diagnosis. Two of these patients died of tumor within the same period, whereas a third patien t has been lost to follow-up. The present cases illustrate an unusual histologic pattern of yolk sac tumor in the mediastinum and highlight the importance of considering this tumor in the differential diagnosis of lesions showing a hepatoid pattern of growth in the mediastinal ar ea.