Malignant mesothelioma: Pathology

Abstract

The majority of malignant mesotheliomas (MMs) occur in the pleura, but they may also arise in the peritoneum, the pericardium, or the tunica vaginalis testis. MM is a great mimic and its morphology is so variable that a vast number of different primary and secondary tumors of the body cavities must be considered in differential diagnosis. Another diagnostic challenge is distinguishing MM from reactive lesions, i.e., epithelioid MM from benign mesothelial hyperplasia and sarcomatoid or desmoplastic MM from fibrous pleuritis. Molecular markers, such as loss of BAP1 and homozygous deletion of 9p21 chromosomal region, have a specificity of 100% and, if combined, a sensitivity of appr. 80% in the diagnosis of malignant mesothelioma. Diffuse MM exhibiting any subtype or morphological pattern may have asbestos etiology.