Patients receive oral imatinib mesylate once daily. Treatment continues in the absence of disease progression or unacceptable toxicity. Patients who achieve a partial response or stable disease with normalization of human chorionic gonadotropin may undergo surgical resection of residual lesions at each tumor status assessment. If residual viable germ cell tumor is present in the resected specimen, patients may resume imatinib mesylate. If no viable germ cell tumor is present in the resected specimen, then no further therapy is administered.