The relationship of pemphigus to neoplasia. A statistically increased incidence of malignancy has been observed in patients with pemphigus. A review of the literature reveals 42 cases of nonthymic malignancies and 18 cases of thymic malignancies. A significant predominance of men, with mean age at onset of 50 years, was observed. Pemphigus vulgaris is more common in patients with nonthymic neoplasms, whereas pemphigus foliaceus or pemphigus erythematosus and pemphigus vulgaris are equally common in patients with thymic neoplasms. Lymphoreticular malignancies, especially Kaposi's sarcoma, are most frequently observed. The majority of patients with nonthymic neoplasms have pemphigus before the detection of the malignancy and have a favorable 5-year survival rate after tumor resection. The majority of the patients with thymic neoplasms have a thymoma before the development of pemphigus. In some patients pemphigus develops after thymectomy and myasthenia gravis is often associated. Overall, 37 of the 60 patients, or 61%, had a neoplasm of the immune system. 