Update on malignant mesothelioma.

Mesotheliomas are uncommon in the United States, with an incidence of about 3,000 new cases per year (or a risk of about 11 per million Americans per year). Incidence and mortality, however, are probably underestimated. Most are associated with asbestos, although some have arisen in ports of prior radiation, and a reported association with simian virus (SV)40 remains controversial. About 85% of mesotheliomas arise in the pleura, about 91% in the peritoneum, and a small percentage in the pericardium or tunica vaginalis testis. The histology of about half of mesotheliomas is epithelial (tubular papillary), with the remainder sarcomatous or mixed. Multicystic mesotheliomas and well-differentiated papillary mesotheliomas are associated with long survival in the absence of treatment and should be excluded from clinical trials intended for the usual rapidly lethal histologic variants of the disease. The median survival is under a year, although longer median survivals for selected patients, particularly those with epithelial histology, have been reported in some combined-modality studies. Recent randomized trials have shown significant improvement in time to progression and survival for the addition of new antifolates to platinum-based chemotherapy.