An intriguing case: malignant mesothelioma presenting as inguinal lymph node metastases.

A 56-year-old woman presented with a right inguinal mass. Biopsy revealed multiple lymph nodes involved with papillary and gland-like structures extending into the surrounding fibroadipose tissue. There was no history of carcinoma or other malignancy. Ultrastructural findings included long microvilli, desmosomes, and tonofilament bundles, indicating metastatic malignant mesothelioma. Malignant mesothelioma only rarely presents as a lymph node metastasis, and electron microscopy is very useful in establishing this diagnosis.