OBJECTIVES: I. Determine the objective response rate in patients with metastatic or recurrent thymoma treated with octreotide. II. Determine the duration of remission in these patients. III. Determine the toxicity of the octreotide regimen in this population. IV. Determine the response rate, duration of remission, survival and toxicity of prednisone added to octreotide in patients with stable disease following octreotide alone.