Primary mediastinal seminoma.

Primary mediastinal seminoma is a rare germ cell neoplasm histologically identical to testicular seminoma. Thirteen patients have been treated with definitive megavoltage radiotherapy at the Stanford University Medical Center, Division of Radiation Therapy, between 1961 and 1976. Doses ranged from 2500 rads over five weeks to 6000 rads over seven weeks. Actuarial survival at ten years is 69% with relapse-free survival of 54%. No patient receiving greater than 4700 rads to the primary lesion had local or systemic relapse. Patterns of relapse and recommendations for diagnostic evaluation are discussed. Primary megavoltage irradiation to the mediastinum and neck with a dose of 4500 to 5000 rads over five to six weeks is appropriate treatment.