Lymphangiomatoid pattern in diffuse malignant mesothelioma of the pleura: a report of six cases.

The multiplicity of epithelioid and mesenchymal forms of diffuse malignant mesothelioma includes patterns that may mimic another process. Identification of the multiplicity of patterns may help in the diagnosis of diffuse malignant mesothelioma. One pattern that has not been described is lymphangiomatoid. We observed six cases with ovoid or elongated or irregular anastomosing vascular-like spaces lined by flattened cells simulating lymphangioma. The luminal spaces could contain proteinaceous material simulating lymph but not erythrocytes. The cells lining the spaces were mesothelial by immunohistochemical staining. The lymphangiomatoid areas never constituted more than 40% of the area of the tumor on the slides. When seen in more solid areas of tumor, the lymphangiomatoid structures generally did not produce diagnostic difficulty. However, when seen at the edge of solid tumor or forming an irregular nodule or invading into adjacent adipose tissue, these lymphangiomatoid structures could be confusing. All six patients had been exposed to asbestos either by occupation or by spousal exposure. Three patients received chemotherapy. One patient died of diffuse malignant mesothelioma of the pleura.