Lymph node metastasis as the initial manifestation of malignant mesothelioma. Report of six cases.

We present six cases in which lymphadenopathy was the initial manifestation of malignant mesothelioma. In five cases, the primary tumor was located in the peritoneum; it was located in the pleura in the sixth. The involved lymph nodes were cervical in four cases, mediastinal in one, and inguinal in one. The morphologic, immunohistochemical, and ultrastructural features were typical of malignant epithelial mesothelioma. A review of the literature disclosed only one previously documented example of this phenomenon. When confronted with a lymph node involved by metastatic tumor, pathologists should be aware that malignant mesothelioma can present initially in the form of lymphadenopathy and include this possibility in the differential diagnosis.